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Heating Degree Days at 65°F (HDD65) is still utilized by ASHRAE Standard 169 for determining Climate Zones and in other fundamental HVAC resources, such as Air Conditioning Contractors of America's (ACCA's) Manual J and S calculations. The U.S. Energy Information Administration (EIA) also uses HDD65 and it even occurs within the Passive House Institute US (PHIUS) where heating is not in demand until Outdoor Air Temperatures (OAT) reach 45°F. This paper explores and supports utilization of Heating Degree Days at 55°F (HDD55) for building energy analysis in heating dominant climates. This is supported by EnergyPlus modeling results for a sample of building types. A degree days overview on Energycap states that "The 65-degree balance point standard was developed 75 years ago to help the gas industry predict heating loads in residences. Studies back then showed that when the average daily temperature fell below 65°F, residences began turning on the heat." Today, HDD65 doesn't reflect structures built to modern energy codes, because internal loads are offsetting thermal envelope losses and when combined with the continued tightening of ventilation energy recovery requirements, heating is not necessary until much cooler than 65°F. According to a Regional Technical Forum (RTF) presentation titled "Overview of Updated Commercial EnergyPlus Building Models and Alignment with CBSA Data" dated August 31, 2021, the 'apparent balance point range between 50-60°F' was the reasonable OAT before heating was utilized by occupants. When energy modeling to HDD65, decisions are being made relative to temperature ranges that have minimal impact on building energy use. For example, when the OAT is in the 50-65°F range, this may mean more economizer hours are available without having to reheat the outdoor air or heat exterior spaces/operating zones. This would decrease the amount of energy the building utilizes, allowing for more accurately sized equipment. Similarly, utilizing Cooling Degree Day's at 50°F (CDD50), as ASHRAE Standard 169 does to determine Climate Zones, to predict cooling loads isn't appropriate as most building types don't need cooling starting at 50°F. Economizers are essentially mandatory for larger buildings which might need cooling at 50oF OAT, but smaller buildings will possibly be in heating mode when the OAT is 50oF. Utilizing CDD in the range of 60-70°F would give a more accurate representation of required cooling loads and will also be a minor focus of this technical paper. New HDD and CDD figures should be produced for ASHRAE Standard 169, Technical Resource Manuals (TRM's), and other publications that utilize degree days. With this information, end users can better analyze the weather's impact on actual building energy usage and better determine equipment sizing and other impacts. [ABSTRACT FROM AUTHOR]

Currently used legacy refrigerants for air conditioning and refrigeration applications such as R-410A, R-404A and R-134a have high global warming potentials (GWP). Due to this, these refrigerants have become targets for phase-down as part of global carbon emission reduction initiatives (Kigali amendment to the Montreal Protocol, EU F-Gas Regulation, etc.). Refrigerant alternatives for existing systems to be used in aftermarket applications are required to be nonflammable. Similar performance in efficiency and capacity while providing a reduction in GWP are required. Refrigerant manufacturers have developed options that attempt to fulfill these needs. However, the reduction in GWP often leads to blends that impose a gliding temperature profile in the heat exchangers besides other factors that need to be considered for drop-in situations like operating pressures, compressor discharge temperatures or material compatibility, among others. This paper evaluates the agreement between different refrigerants and the requirements for existing legacy refrigerants in air conditioning and refrigeration applications. A focus on temperature glide and inherent performance impact is evaluated and related to possible considerations for use. Refrigerant options with similar performance and operating characteristics for R-410A, R-404A and R-134a are identified with R-466A, R-448A/R-449A/R-407H and R-513A/R-456A, respectively. A close evaluation of material compatibility and detailed system modeling beyond this screening evaluation are needed to confirm viability for the specific application. [ABSTRACT FROM AUTHOR]

In 2016, Kujak presented a current state of how to apply hydrocarbon safely per standards consideration and methodologies for direct expansion air conditioning applications. Refrigerant charge limits at the time were very restrictive and did not allow for larger capacity direct refrigerant expansion systems. In recent years, the HVACR industry has been actively investigating the safety of flammable refrigerants by determining their risks, potential occurrences and severity of events and hydrocarbon refrigerant charges have increased significantly. This paper will provide an updated view of the selection challenges faced by air conditioning product designers and compare the various flammability characteristics of R290 compared to R454B. It will give an updated overview of standards methodology to determine the refrigerant charge and resulting cooling load to compare various flammable refrigerants for ASHRAE 34 Standard Class 2L, 2 and 3 refrigerants. In addition, the authors investigated the optimization of blends using R290, R1270 and RE170 to understand if there are possible optimization of properties and flammability limits to increase refrigerant charges. [ABSTRACT FROM AUTHOR]

In 2019, when electrical system energy losses are included, about 39% of the total U.S. end-use energy was consumed by the residential and commercial buildings according to EIA. Thus, advanced and optimal operations in building energy systems will reduce their energy uses and improve indoor environmental conditions. To achieve optimal performance in the building systems, accurate components models became crucial to predict the system's performance and finally optimize it. This paper proposes an integrated two-level optimization approach to optimize the performance of the chilled water VAV system and a packaged DX VAV system. The first level of optimization is a Component Model Optimization (CMO) using genetic algorithm (GA). The optimization algorithm will determine the optimal model structures for accurate component modeling. Also, a parametric study was conducted to select the best model structure and validate the optimization process results. The second level of optimization is System Performance Optimization (SPO). The SPO was conducted by creating an optimization algorithm that will integrate the output of all the created component models. The output of the data-driven models will be optimized to be eventually used to optimize the set points of the whole system. The setpoints that were chosen to be optimized for this paper are the supply air temperature (SA) and the static duct pressure (PS). The testing results show that the proposed models can accurately predict system performance. Moreover, the two-level optimization process has resulted in a 25% and 22% savings in the fan power consumption and the reheat energy, respectively, when compared against the baseline case that was selected for this study. Also, this paper has validated the use of such data-driven models that can help in developing several aspects of the industry. [ABSTRACT FROM AUTHOR]

Fan coil units (FCUs) are decentralized air-conditioning devices to locally condition zone air. In the U.S. and Europe, FCUs are widely deployed in diverse types of buildings such as offices, hotels, schools, and residential apartments because of their low cost and easy installation. The abnormal operation of FCUs due to faults or malfunctioning components may cause significant energy waste and degrading thermal comforts. However, faults occurring in FCUs have been seldom investigated. A systematic analysis of fault impacts of FCUs would enable a better understanding of fault impacts, an efficient development of fault diagnostics approaches, and an improvement of FCUs monitoring system design. In this paper, we used a FCU simulation model, which was developed in the HVACSIM+ environment from a previous study to evaluate FCU fault impacts. Five common faults with different intensities were simulated within a one-year time window to generate fault inclusive operation data. We employed a bottom-up fault impact analysis framework. Fault effects on multiple measurements were firstly evaluated to obtain fault symptom occurrence probability distributions which quantify measurements' sensitivities. Secondly, fault thermal comfort impact and fan power energy consumption impact were assessed. Lastly, the result from fault thermal comfort impacts and energy penalties was used to rank FCU faults. [ABSTRACT FROM AUTHOR]

Aligning with the global movements towards mitigating CO2 emissions and regulations to phase-down HFC refrigerants, many low-Global Warming Potential (GWP) refrigerants are being tested and proposed as fourth-generation refrigerants. R1234yf (HFO-1234yf) is a refrigerant with GWP <1 (0.31) and has replaced R134a (HFC-134a), which has GWP 1300, in automobile air conditioning systems and has a high potential to replace it in domestic refrigerators. In this paper, an energy performance evaluation and a life cycle climate performance assessment for R1234yf were conducted and compared to R134a. The study involved two identical domestic refrigerators with the same refrigerant charge that is recommended by the manufacturer. R1234yf showed resulted in similar cabinets air and refrigerant temperatures. However, the discharge temperature for the R1234yf refrigerator was relatively higher temperature than that for R134a. Also, R1234yf demonstrated higher daily energy consumption and more extended compressor run-time than of R134a. On the other hand, R1234yf proved significantly lower direct emissions and higher indirect emissions than those caused by R134a. Overall, R1234yf resulted in 3% reduction in the Lifecycle Climate Performance (LCCP) CO2 emissions compared to R134a. [ABSTRACT FROM AUTHOR]

AHRTI (Air-Conditioning Research Technology Institute) sponsored a research program on developing essential low global warming potential (GWP) refrigerant database in collaboration with Oak Ridge National Laboratory (ORNL) and National Institute of Standards and Technology (NIST). In 2019, AHRTI received a US Department of Energy Building Technology Office funding award to carry out this research program. As part of the overall effort, Trane Technologies conducted AHRTI Project 9016 - Chemical Stability of Low GWP Refrigerants with Lubricants. This paper summarizes a subset of AHRTI Project 9016 results of highly accelerated life tests (HALT), conducted according to ASHRAE Standard 97 sealed glass tube methodology, for refrigerants R-1336mzz(Z), R-1336mzz(E), R-514A, R-1233zd(E), and R-1224yd(Z) with and without lubricants. [ABSTRACT FROM AUTHOR]

Delhi Metro is India's first modern public transportation system and the world’s 8th longest metro system with network length of 347.6 kilometers (215.9 miles) and 253 stations. The total energy consumption for running of trains and auxiliary systems was 1117 million kWh in the year 2018-19. The electrical and mechanical equipment at stations consumes about 40% of the total energy consumption of the entire network. An underground station consumes about 8 to 10 times of energy than an elevated station because of air conditioning and lighting requirements. The Environment Control System (ECS) or Ventilation, and Air-Conditioning (VAC) systems consumes approximately 70% of total energy consumption at an underground station. The Air Handling Units (AHUs) and Trackway Exhaust Fans (TEFs) which consumes about 50% of total energy consumption of VAC systems are selected on the basis of Open Mode, Close Mode and Emergency Mode operations which requires different pressure rating of the fans in different modes. During implementation of Phase-I and Phase-II of Delhi MRTS, the AHUs and TEFs were fixed speed type and consumes more power because of selection of fans at higher pressure rating. In Phase-III, all the 34 underground stations are provided with Variable Frequency Drives (VFDs) for AHUs and TEFs which resulted in the huge amount of energy savings at the underground stations as the fans can be operated with required pressure rating as per the mode. Further, Ministry of Housing & Urban Affairs, Government of India, in their publication titled ‘Best Practices & Innovations in Metro Rail Systems’ have acknowledged this endeavour of Delhi Metro and suggested all metros in India to provide their systems with VFDs. The actual energy savings to the tune of 35% or more are realized with the use of VFDs. This paper presents a detailed comparative study between VFD system and fixed speed system based on actual energy consumption at underground stations of Delhi Metro. The control algorithms designed to vary the speed along with the other intelligent features implemented in the station’s Building Management Systems for energy savings are also presented. The paper also discusses the design basis for selection of the various equipment used in VAC systems at underground stations. [ABSTRACT FROM AUTHOR]

Heating, Ventilation, and Air Conditioning (HVAC) systems operate at dynamic loads and may present unpredictable disturbances. Relatively minor disturbances can greatly affect the performance of certain subsystems, such as the cooling coil control valve. The operating error of the cooling coil control valve has the potential to compound with error from other subsystems and deteriorate the performance of the air handling unit (AHU). In many cases, the control systems are nonlinear and of high order, which reduces the likelihood of system stability with conventional control approaches. The objective of this paper is to experimentally evaluate the cooling coil control valve performance of cascade control by comparing it with a conventional Proportional- Integral (PI) control, on a nonlinear cooling coil control system. In the paper, the performances of both controls were compared first using a step change in reference input, i.e. supply air temperature setpoint step change and a step change in disturbance input, such as chilled water loop differential pressure (DP) step change. The primary testing criterion is the operating error, in terms of mean integral square error (mISE). System stability, settling time, and disturbance rejection are also considered in the comparison of the two control approaches. As a result, the cascade control is found to be the most effective when the valve system experiences pressure interruptions. For example, a maximum error of 0.46 °F for the cascade control and 0.95 °F for the single loop control were observed when the DP is reduced by 5 psi (27.8% of the operation value), while the mISE in the cascade control was only 5.5% of the single loop mISE. In addition, the mISE value of the cascade control is approximately 42% of the single loop mISE value for reference step change test. [ABSTRACT FROM AUTHOR]

Anyone who has had the opportunity to work in the Controlled Environment Agriculture (CEA) industry knows that managing the latent load of an operation is paramount to its success. For a plant to grow and thrive, it must pull water and nutrients from the growing medium, through its roots and up its stem to eventually transfer the nutrients into its growing tissue. To complete the process, this internal water must finally be exposed to the open air so it can evaporate away. A CEA facility is a farm operation that is fully contained indoors where light, temperature, relative humidity, and the atmosphere can be controlled. Most cannabis CEA facilities introduce supplemental carbon dioxide to encourage plant growth. Because of this, the grow rooms are sealed with minimal to no outside air to prevent exhausting valuable carbon dioxide. If latent removal capacity is insufficient, the relative humidity in the space quickly reaches saturation levels and the plant can no longer move water from roots to air. This can cause serious plant health issues that can eventually lead to death of the plant. Every pint of water placed in the growing medium that does not drain to waste outside the room must, eventually, be removed from the air. Sensible loads in a CEA operation are fairly easy to determine and handle due to the large lighting loads (20 – 50 watts/ft² ), but when the lights go off, it’s a different story. During the simulated nighttime, the plants reduce the amount of water they deliver to the air, but it does not disappear. Without the sensible load of the lighting system to drive the latent capacity of air conditioning, dedicated dehumidification must be used to control relative humidity. A high efficiency dehumidification system is vital to minimize the total electric consumption of the operation. This paper explores a comparative energy analysis of various dehumidification technologies used in CEA operations. The primary systems to be examined will be integrated HVAC systems with on-site heat recovery to achieve dehumidification reheat, chilled water systems with on-site heat recovery to achieve dehumidification reheat, solid or liquid desiccant dehumidification systems, and high efficiency stand-alone dehumidifiers as defined by California’s Title 24 proposed regulations for dehumidification efficiency in CEA facilities. Title 24 is a code for CEA facilities that governs dehumidification efficiency, lighting efficiency, and requirements for greenhouses. When possible, minimum allowed efficiencies and actual equipment efficiencies will be used. This analysis will focus on CEA cannabis operations, but the results could be applied to other crops, as well. [ABSTRACT FROM AUTHOR]

Heating, Ventilation and Air conditioning (HVAC) systems account for approximately 40% of the total energy used by buildings in the USA. To reduce this consumption States enforce minimum energy codes that currently range from strict (ASHRAE 90.1-2016) to relaxed (ASHRAE 90.1- 2007) with some states following no particular standard. To reach as close as possible to net zero carbon and energy, each statewide energy code requires different levels of interventions for each code minimum building. This paper presents a collection of potential HVAC retrofits to transition each State’s current code minimum buildings towards the goal of net zero to achieve a carbon free future by 2050. The study shall use a large array of code minimum criteria and climate zones covering the 48 contiguous United States to determine the most successful interventions at reducing the energy use of buildings meeting today's energy codes. Office use type has been selected for the study as they account for 18% of total buildings and close to 19% of the total commercial floorspace. A number of interventions will be applied to this use type that will vary based on current code and climate zone; however, a common theme will be electrification through the use of heat pump technology. Each intervention will be scored based on energy and carbon savings, along with level of difficulty and cost. The study not only provides a comprehensive transition guideline toward the net zero energy and carbon but also predicts the future project opportunities. [ABSTRACT FROM AUTHOR]

Current rating standards for residential, electric-driven vapor compression systems determine seasonal energy efficiency (e.g., SEER) using a bin method along with equipment performance data from steady-state tests at different operating conditions. These standards were originally developed for equipment with single or two-stage thermostat control but have been incrementally updated to include equipment with advanced controls and variable-speed compressors and fans. However, the controls are overridden during equipment testing and therefore the rated performance does not consider the interaction of the integrated controls, equipment, and building dynamics. As a result, the standard ratings do not fully capture the characteristics of part-load operation and do not necessarily reward equipment with superior controllers. To address these issues, a load-based testing methodology has recently been developed for estimating the seasonal performance of variable-capacity cooling and heating equipment. The load-based testing methodology emulates the response of building sensible and latent loads to the equipment controls in a psychrometric test chamber by continuously updating the room temperature and humidity based on a virtual building model. The test unit thermostat naturally responds to the dynamic temperature variation and controls the equipment capacity in response to a deviation from its setpoint. The test unit thermostat is installed in a thermostat environment emulator to provide a standardized environment to the thermostat in order to ensure realistic and reproducible conditions for the thermostat. This enables the load-based testing procedure to capture realistic control interactions and performance of a heat pump in a laboratory using psychrometric test chambers. However, to adopt the developed methodology for nextgeneration rating standards, it is crucial to assess the repeatability and reproducibility of the load-based testing approach. In this paper, the assessment of the repeatability of the load-based testing methodology for a 3-ton variable-speed heat-pump operating in cooling mode is presented. The test unit performance was measured multiple times in the same psychrometric facility based on the load-based testing approach. A comparison of the test equipment estimated seasonal performance for different sets of tests is presented along with a discussion of the causes for the differences. [ABSTRACT FROM AUTHOR]

Insulated ducts are extensively used for building air-conditioning applications. The insulation levels are designed based on energy loss considerations while the level of insulation required to prevent condensation on the duct surface from the air surrounding the duct is often not evaluated. In this paper, a coupled heat-mass transfer model has been developed to model the condensation-evaporation on vertical duct surfaces with for ducts within stud-bays (cavities) located adjacent to the conditioned building envelope. California Building Energy Code Compliance-Residential (CBECC-Res) building simulation tool was used to calculate the indoor space conditions for a single-family home located in sixteen different Climate Zones (CZ) of California. The simulations indicated that an increase in the area available for air infiltration in the cavity can increase condensation, however, the duration for which condensed water is present on the duct decreases. The quantity of water condensed on uninsulated ducts with low emissivity surfaces (ε close to zero) is much higher than that for high emissivity (ε=0.9) ducts (twice as high for reference CZ 13, Fresno). Furthermore, insulating the duct reduced condensation significantly and for CZ 13, R-1 insulation is sufficient to eliminate condensation completely. The worst-case scenario (low emissivity, uninsulated duct in a cavity with a large area for infiltration) was modeled for all climate zones. The climate zone with the highest level of condensation is CZ 9 (Burbank) i.e. 0.0081 lb. (0.037 kg), while the condensation was lowest for CZ 2 (Santa Rosa). Overall, the amount of water condensed, even in the worst-case scenario, is small compared to the moisture already present in the wooden studs surrounding the duct. [ABSTRACT FROM AUTHOR]

Variable Refrigerant Flow (VRF) systems are gaining popularity in multizone commercial buildings due to comfort advantages owing to modulation and tighter temperature control. However, their actual installed performance in terms of energy efficiency, economic and environmental benefits relative to conventional heating, ventilating, and air conditioning (HVAC) systems are not well documented. It has become crucial to develop a validated methodology to accurately predict their seasonal performance to support facility owners and designers in decision-making and equipment sizing. Gas Engine-driven Heat Pump VRF (GVRF) systems are relatively new in the North American market and there are limited data on their installed performance characteristics across a wide range of conditions. Heat pump specifications are typically based on single-point rating conditions, whereas the actual installed performance of all air-source heat pumps, both gas-fired and electric, are dependent on ambient conditions and part-load operation. The efficiencies of these equipment are best defined by performance maps ranging across a broad range of operating conditions. The objective of this paper is to describe the development of EVRF (Electric VRF) and GVRF EnergyPlus models using the System Curve-based Model approach based on multiple custom performance curves. The study also highlights the current limitations of modeling VRF performance using manufacturer performance data as they inherently operate at part-loads below 50% when sized to meet the heating load in cold climates, but manufacturer specified performance data are frequently not specified below part-loads of 60%. The modeled performance curves were compared with measured performance data generated in field demonstrations. These preliminary models were used to predict seasonal performance and operating cost savings of GVRF systems paired with dedicated outdoor air system (DOAS) relative to electric VRF/DOAS systems and baseline variable-air-volume (VAV) systems. This comparison was done for two commercial Department of Energy (DOE) reference building types across five ASHRAE climate zones in North America. Results indicate that the GVRF/DOAS may reduce peak electric demand by 24%-96% in all simulated applications and lower annual energy costs. Due to high-efficiency heating and cooling, GVRF/DOAS also has potential to reduce GHG emissions compared to conventional VAV systems given the current electricity generation mix. The results of these studies show the potential for VRF heat pumps, but also point to a need for additional measured field data for both EVRF and GVRF to build confidence in the predictions of the current VRF models. [ABSTRACT FROM AUTHOR]

Most air conditioning and refrigeration systems that employ the vapor compression cycle rely on oil circulating with refrigerant to lubricate the bearings and other contact surfaces in the compressor. The lubricant acts as a sealant to reduce leakage losses during the compression process and it also helps to absorb some of the excess heat that is generated in the compression chamber. However, this oil circulation results in oil retention in various other components outside the compressor depending on the physical interaction between lubricant and refrigerant and their transport properties. Other factors, such as the geometry and orientation of connecting lines, and the system operating conditions, such as refrigerant flow rate and oil circulation ratio, also impact the oil retention. Because of oil retention, the efficiency of heat exchangers (evaporators and condensers) decreases. In addition, the oil level in the compressor reduces, which may ultimately affect its efficiency and life span. The current line sizing rules reported in the ASHRAE Handbook Refrigeration have only limited consideration of the effects of oil in the system. With the increasing development of variable-speed systems as well as future use of newer HFO refrigerants, there is a need in the industry for upgrading the line sizing recommendations, especially the connecting gas lines of unitary split systems, which consider the effects of oil retention. To develop these rules, measuring oil retention at different operating conditions is important. A test setup has been built to measure oil retention in horizontal and vertical lines of different diameters at different refrigerant and oil flow conditions. Initial results for R134a-POE32 are presented in this paper. Based on the collected data, the final goal is to build a model, which can predict oil retention in gas lines for some of the commonly used refrigerant-lubricant combinations in the HVAC&R industry. [ABSTRACT FROM AUTHOR]

One of the critical tasks of the International Energy Agency's Energy Conservation in Buildings and Communities (IEC ECBC) Program's Annex 61, "Business and Technical Concepts for Deep Energy Retrofit (DER) of Public Buildings" is to develop bundles of core technologies (measures), which, when applied in major renovation projects to older (pre-1980) buildings, allow site energy reduction by 50% or better compared to the pre-renovation baseline. A short list of these technologies has been generated through an analysis of DER projects. Characteristics of some of these core technologies depend on technologies available on an individual nation's market, minimum requirements of national standards, and lifecycle cost (LCC) analysis. In addition to these factors, requirements for building envelope-related technologies (e.g., insulation levels, windows) depend on specific climate conditions. Previously, results published in a paper entitled "Parametric Study of Core Energy Efficiency Measures Used in Deep Energy Retrofits for Barracks and Office Facilities" showed that typical renovations that meet only the minimum code requirements of ASHRAE Standard 90.1-2010 result in reduction of building energy use (including plug loads) in Climate Zones 1 through 8 by only 8% to 16% compared to the baseline in barracks and by 8% to 22% in administrative buildings. With a DER scenario, heating energy can be further reduced, reaching 87% to 90% reduction in barracks and by 63% to 87% in administrative buildings. Cooling energy can be reduced by 60% to 67% in barracks and by 51 to 58% in administrative buildings. Reduction of lighting energy in barracks and administrative buildings will be 50% and 22%, respectively. The major part of remaining energy consumption in barracks is due to energy use by plug loads and heating of the domestic hot water (DHW). In administrative buildings, the major remaining part is due to plug loads. Barracks and office facilities have relatively low ventilation and internal loads compared with dining facilities, which raises the question about whether the core technologies used for them will be as effective in buildings with higher ventilation and internal loads. This paper shows that application of a core technologies bundle to dining facilities, which have high process loads and ventilation requirements, significantly improves energy use in the building compared to the typical renovation scenario but does not come close to requirements of DER. A DER of a dining facility (DFAC) is a very capital-intense proposition when compared to barracks and administration buildings. Further energy use reduction requires selection of energy-efficient process equipment and improvements in ventilation systems (hood capture efficiency improvement, exhaust air heat recovery, and use of ventilation system demand control). Additional energy saving can come from dishwasher greywater heat recovery. [ABSTRACT FROM AUTHOR]

Dehumidifiers (DHUs) are the second most-selected equipment, after air conditioning (AC), used to manage indoor relative humidity (RH) in homes. They can offer the lowest first-cost, are well-established in the market, and are often easier to install than other supplemental dehumidification alternatives. However, DHUs have the potential to use significant amounts energy and may impact the performance of the central ducted cooling system under certain conditions. Dehumidifiers may be designed to be ducted or un-ducted. Dehumidifiers with ducts are sometimes referred to as whole-house or ducted dehumidifiers. Manufacturer manuals offer several different options for ducting DHUs, but they do not provide adequate information about potential performance impacts. Also sorely missing are expanded DHU performance metrics to help professionals and consumers determine the appropriate DHU capacity and to help predict operational efficiency for specific realistic applications. The Florida Building Commission initiated a research project to determine if some common ducted DHU configurations had significant energy and moisture impacts and whether any configurations should be not allowed in Florida Building Code. The research evaluated measured energy use and latent heat removal rates of AC and DHU for four different common ducted DHU duct configurations. Testing occurred during variable weather and interior latent loads common in a warm moist climate. A highly-instrumented building lab was used to evaluate AC and DHU performance based upon how a DHU was ducted to a central AC ductwork and compared these to a DHU ducted to and from an open central room. There was less than 1% difference in annual space conditioning energy (DHU + AC) among two different methods of DHU ducted to the central supply duct and the DHU ducted directly to indoors. However, steady-state and longer-term test findings showed that a DHU ducted to and from a central cooling system return upstream of the central cooling evaporator coil resulted in the annual predicted space conditioning energy use of 308 kWh/year (4%) more than the DHU ducted directly to indoors. It also resulted in decreased central AC latent performance by 28% when the DHU and AC ran simultaneously. This DHU duct configuration further degraded dehumidification performance by causing moisture to be evaporated off of the central cooling coil at a rate as high as 2-3 pounds of water per hour when the AC was cycled off and DHU operated. This paper discusses the experimental method, results and recommended practice of ducting DHU for optimum performance. [ABSTRACT FROM AUTHOR]

Ground Source Heat Pump (GSHP) systems are known to have an enormous potential for energy savings due to their ability to achieve higher system efficiencies. Their energy-saving potential, however, varies depending on many factors, such as the appropriate design and control, regular maintenance, and the locations and types of the buildings served. A vast amount of research was focused on the design and control aspects of this type of system, but the impacts of a building itself including its type and location on the energy savings of GSHP systems are usually neglected. This paper, therefore, aims to find out the relationship between the type and location of a building and its potential energy savings when a GSHP is used through real measurements and numerical simulations. To do so, three different types of buildings that are equipped with GSHP systems in a cold climate region are studied, including a fire station, a church building, and a small office. These buildings are selected in this study by considering their distinct operating schedules, which may have a significant impact on building energy consumption and savings. Actual utility bills that were obtained from building owners are used to calibrate the numerical simulation models established for these three buildings. These calibrated models are then used to identify the potential energy savings when comparing them with baseline buildings that are equipped with conventional HVAC (Heating, Ventilation, and Air Conditioning) systems (according to the ASHRAE 90.1). The impact of building locations on energy savings is investigated by locating these three buildings from their original place (ASHRAE Climate Zone 7) to other different climate zones. The result of this study shows that “all the climate zones are suitable for the application of GSHP systems in the United States”, but the energy-saving potential of GSHP systems varies with building type and location (climate zone). Among the buildings investigated, the church building has the potential for achieving higher energy savings by using GSHP systems. This study is expected to be helpful for designers and building owners to make a decision rationally on if GSHP systems are appropriate for their projects, especially in consideration of the relatively high investment of this type of system compared to other commonly-used HVAC systems. [ABSTRACT FROM AUTHOR]

Recent advancements in the field of mobile air conditioning and refrigeration have witnessed an extensive use of the swash plate compressor due to its compact structure, continuous operation, small size, light weight and better thermal comfort inside the vehicle. The design of the swash plate compressor is complex so that it requires considerable contributions from different fields of engineering viz. engineering mechanics, heat transfer and fluid dynamics. An estimate of compressor performance through an analytical/mathematical model at the early stages of design and development serves as a useful tool for the designer. The input power, refrigerant mass flow rate, compression ratio and volumetric efficiency are important parameters to characterise the compressor performance. This paper presents an analytical/mathematical model for a 10-cylinder swash plate compressor with the emphasis on predicting its performance in terms of shaft torque and mass flow rate for a given rpm. A kinematic model is developed to obtain the piston displacement as an explicit function of angle of rotation of the swash plate. The model of piston and swash plate dynamics is developed then by analysing the interactions between forces and moments. The compression process model is formulated to determine the temperature and pressure inside the cylinder during one revolution of the swash plate along with the total mass flow rate in and out of the compressor. A time-varying model for the compressor is developed by combining the above three sub-models. Some experimental validation comparing predicted and measured drive torque has been done to verify the analytical/mathematical model. The predicted torque is in close agreement with the measured value. [ABSTRACT FROM AUTHOR]

As environmental concerns and accompanying regulations grow around the world, the Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC&R) industry is working to develop technologies that utilize low-global warming potential (GWP) refrigerants and remain within competitive coefficient of performance (COP) values of previous hydrofluorocarbon (HFC) systems. Carbon Dioxide (CO2) has been investigated extensively in the past 25 years as a potential substitute for HFCs in refrigeration application in mild ambient climates. In efforts to increase the efficiency of CO2 systems, researchers and industry have identified cycle modifications that are particularly beneficial in transcritical CO2 cycle application, such as expansion work recovery and economization. This paper presents an overview of the design and operation of a multi-stage transcritical CO2 cycle with two independentlycontrolled evaporators. The cycle utilizes three stages of compression with intercooling between the second and third stages, as well as flash tank economization at each evaporator, including evaporator bypass lines for vapor from the flash tank. Furthermore, the cycle was designed to allow transition between methods of expansion work recovery without the need to stop the compressors. The cycle can switch between electronic expansion valve (EXV) mode, ejector mode, and a turbomachine expander mode with the actuation of several ball valves mid-operation. The purpose of this work is to describe the theory and rationale behind system design, discuss how the test stand will be controlled, and provide instruction on the transition between expansion methods without shutting down the compressors. [ABSTRACT FROM AUTHOR]

When I joined a hermetic compressor company as a research chemist back in the early 1980's I was quickly introduced to ASHRAE. The first project I worked on was to construct a manifold assembly used to make glass sealed tubes based on ASHRAE Standard 97. Years later I was attending ASHRAE conferences and sitting in on various technical committees dealing with refrigerants, lubricants, contaminant control and system chemistry; listening to what was going on in the refrigeration and air conditioning industry. I was introduced to individuals who were working on similar projects that I was and learned how ASHRAE research worked, the value of handbook chapters, various programs I could attend and yes how standards where developed and implement like what I learned in Standard 97. 35 years later I find myself still in the industry utilizing ASHRAE, have a son that is also in the industry and now I try to be a leader and mentor. This paper will focus on what I have learned over the years that has helped me and my industry peers advance the art. Will look back to how these functions have been shaped and look forward to what's next. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of using a Tesla turbine as an alternative air-conditioning compressor drive unit in vehicles as an example rather than the traditional method of linking the compressor rotor to the vehicle engine crankshaft belt or chain. Interest in Tesla turbines has recently gained momentum because of the possibility of obtaining high efficiency in energy conversion, as claimed by the inventor Nikola Tesla. This paper investigates the possibility of driving the air-conditioning compressor using the hydraulic energy available in the engine lubrication oil piping provided by the engine oil pump. The engine oil pressure can be used to drive the Tesla turbine driving the compressor. Tesla turbines, also known as bladeless or boundary layer turbines, were invented in the early twentieth century but were never commercially exploited. Tesla turbines are known for their ease of construction and low erosion rate, because the rotating parts experience no direct impact from fluid-borne abrasive matter. For this research, a software package was used to create the model. Computational fluid dynamics (CFD) simulations were conducted by varying turbine inlet fluid flow rate, turbine inter-disk spacing, and turbine disk outlet opening diameter. The results are shown in tables and graphs presented in this paper. Selected graphical presentation showing fluid streamlines and the turbine/oil flow physics are included. Results are discussed for the turbine suitability as a drive unit for the air-conditioning compressor. This investigation shows that Tesla turbines are not suitable for automotive air-conditioning compressors when powered by relatively low-pressure engine oil flow rate supplied by the engine oil pump. This investigation also shows that the performance of such machines can be influenced by a number of factors, such as inter-disk spacing, fluid viscosity, and turbine disk opening diameter. Efficiency of Tesla turbine drives can be enhanced by harmoniously matching these factors. Tesla turbines are easy to manufacture and are suitable for energy recovery where high mass flow rate is available for using as turbine driving fluid. Tesla turbines are easy to adapt and can cover a range of flow rate capacities. Using such a system for energy conversion can lower capital equipment costs and improve the turbine lifespan, contributing to sustainable engineering development. [ABSTRACT FROM AUTHOR]

The Kigali amendment to the Montreal Protocol will require the phase out of R410A used in air conditioning systems in developed countries by the late 2020s. The HVAC&R industry will therefore need to begin using R410A replacements by the mid 2020s. Alternatives for R410A with lower global warming potentials (GWP) have been studied extensively over the past few years with limited success in finding an optimal replacement. A number of near design-compatible candidates (close match in capacity, efficiency, and other factors) have been proposed and evaluated, including R32, R452B, R454B, HPR2A, ARM-71a, and R447B. These fluids are all classified as “2L” flammable. This paper reports the characteristics and performance of a new and innovative R410A alternative in two air conditioning platforms. System performance measurements with this new refrigerant are presented for a 100 RT air-cooled packaged water chiller along with R410A as baseline, as well as R32 and R452B. The chiller comprised scroll compressors, a brazed plate evaporator, and microchannel condenser. Also, system performance results with the new refrigerant are presented for a 3 RT residential split system along with R410A as baseline. The new refrigerant was designed to be compatible with existing R-410A equipment, requiring minimal modifications to equipment for air conditioning and heat pump applications. [ABSTRACT FROM AUTHOR]

The goal of this project is to use cost-effective dehumidification to reduce the latent heating load on air conditioning units, thereby improving energy efficiency and reducing power consumption. Given the proprietary information surrounding desiccant wheels, there exists considerable opportunities for alternative desiccant dehumidification systems. This paper investigates the application of inexpensive silica gel desiccant for dehumidification of commercial and institutional buildings. We demonstrate the use of silica gel beads in a custom rotary belt device, installed as a retrofit to the air conditioning system of a warehouse building. Operation, design, and theoretical energy savings are presented. Preliminary test results are presented showing the influence of key operating parameters including temperature of the regeneration air stream, rotation speed of the belt, and mass of desiccant relative to air volume. Performance of the unit under different weather conditions reveals that the current design can achieve up to 1.6 Btu/cfm of energy savings per year, as compared to the theoretical limit of 2.9 Btu/cfm. The scalability of such a unit offers promise in energy savings for medium and large scale commercial applications. [ABSTRACT FROM AUTHOR]

The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) announced an industry-wide cooperative research program to evaluate alternative refrigerants that have low global warming potential (GWP). This paper presents testing results for the performance of an air conditioner and a heat pump using three low GWP refrigerants (R32, D2Y-60 and L-41A) and R410A. The results show R32 and L-41A are good replacement candidates for R-410A. The paper also presents thermophysical property differences the four refrigerants. The paper also presents the cycle modeling which was used to investigate soft-optimization for D2Y60. [ABSTRACT FROM AUTHOR]

Refrigerants are the life-blood of vapor compression systems that are widely used in Heating, Ventilation, Air-Conditioning, and Refrigeration (HVAC&R) applications. The HVAC&R community is currently transitioning from mainstream refrigerants that have high Global Warming Potential (GWP) to alternative lower-GWP refrigerants. During this transition, it is important to account for the life cycle climate performance of alternative refrigerants since their performance will be different than that of higher-GWP refrigerants. This requires the evaluation of the system performance with the new refrigerants. Unfortunately, it is extremely difficult to predict the realistic performance of new alternative refrigerants without experimental validation. One of the main challenges in this regard is modeling the compressor performance with high fidelity due to the complex interaction of operating parameters, geometry, boundary conditions, and fluid properties. High fidelity compressor models are computationally expensive and require significant pre-processing to evaluate the performance of alternative refrigerants. This paper presents a new approach to modeling compressor performance when alternative refrigerants are used. The new modeling concept relies on using existing compressor performance to create an approximate model that captures the dependence of compressor performance on key operating parameters and fluid properties. The model can be built using a myriad of approximation techniques. This paper focuses on Kriging-based techniques to develop higher fidelity approximate scroll compressor models. Baseline and at least one alternative refrigerant performance data are used to build the model. The model accuracy was evaluated by comparing the model results with compressor performance data using other refrigerants. Preliminary results show that the approximate model can predict the compressor mass flow rate and power within ±5%. [ABSTRACT FROM AUTHOR]

In the research reported in this paper, a performance model capable of characterizing parallel fan-powered terminal units (FPTUs) in the variable-airflow operation was developed by assembling its component models (a heating coil, a mixer, and a variable-speed fan) in a mass and energy balance approach. Two configurations of parallel FPTUs with different heating coil locations were considered. In addition, the performance impact of the air leakage from the FPTU housing to the plenum space was captured by integrating a leakage fraction into the model development. To demonstrate the use of the developed model, sample calculation results with four air leakage levels are provided over heating and cooling operating ranges, along with the equations for the model implementation. Incorporating the variable-airflow operation and air leakage allows the developed model to accurately represent the performance of parallel FPTUs at realistic operating conditions. This cannot currently be achieved using existing building energy simulation tools due to the exclusion of the variable-speed fan and air leakage in the performance modeling. [ABSTRACT FROM AUTHOR]

This paper presents a case study of a new ten story 83,700 ft² (7780 m²) office building in downtown Tokyo with a mix-mode ventilation system from the mechanical designer's point of view. Natural ventilation (NV) is an effective method to reduce the energy consumption of buildings by turning off the operation of air conditioner. This technique has been practiced for decades in Japan but it has rarely been realized at a tenant office building in a dense city where multiple tenants occupy the building. In this paper, the design approach of the natural ventilation system integrated to the building and its overall system is presented. [ABSTRACT FROM AUTHOR]

This paper explores how barometric pressure, air temperature, and air temperature difference affect any sensible cooling process. In data centers, the equations presented apply to the heat rejection that occurs within air-cooled servers and air-handling units used to remove the heat from the building. In this paper the focus will be on the air handlers, however the same equations are applicable to the servers The purpose of this paper is solely to bring together in one place some relevant equations, tables, and graphs that will assist engineers that are designing or evaluating sensible heat rejection systems. To be clear, the equations presented in this paper are applicable only when there is no moisture condensed in the cooling process. * A small change in air handler or server operating delta t (Δt) from 20°F (11.1°C) to 22°F (12.2°C) results in a reduction of 9.1% in required cooling airflow for the respective air handler or server. * Most cities experience normal drops in barometric pressure during the year equivalent to a 500 to 1000 ft (152.4 to 304.8 m) increase in altitude, resulting in the need for cooling air to increase by 2% to 3.5%. [ABSTRACT FROM AUTHOR]

In building space conditioning vapor compression cycles provide cooling. The working fluid is often a refrigerant that has good thermal and transport properties and high volumetric capacity for AC applications, but it might have unfavorable effects on the environment in case of leakage. Energy conservation and environmental concerns are the core reasons for the tremendous growth of high performance and environmentally friendly heat transfer fluids. This paper presents data of the thermal performance of four Low Global Warming Potential (LGWP) refrigerants, that is, refrigerant R32 (GWP ~ 675), R1234yf (GWP ~ 4) and two new developmental refrigerants that have GWPs of about 300 and 500. The fluids investigated in this work replaced refrigerant R410A (GWP ~ 2088) in a ducted split system for residential air conditioning applications. The COPs, cooling capacities, refrigerants thermodynamic cycles characteristics are discussed in details in this paper and for a broad range of ambient temperatures; especially for extreme high temperature conditions of 110° and 115°F (43° and 46°C). Refrigerant R1234yf had an intriguing behavior when compared to R410A. This refrigerant had slightly lower COP at mild ambient temperatures but higher COPs at high ambient conditions. However, by adopting the same system, R1234yf provided only about 54% of the nominal capacity of the AC unit. R32 had a higher capacity and similar COPs as that of R410A but its discharge temperatures and pressures were significantly higher. The two novel developmental refrigerants yielded good COPs and cooling capacities with similar cycle pressures and compressor discharge temperatures. The charge of DR-4 in the system had to be carefully adjusted for the tests at high temperature ambient conditions. With minor adjustments of the expansion valve of the unit, the refrigeration cycles with the two new developmental refrigerants were optimally controlled and further improvements of the capacity and COPs were achieved. [ABSTRACT FROM AUTHOR]

Building air distribution terminal system designers and system installers require accurate quantitative information on the diffuser throw and pressure loss performance of the installed system to achieve optimum efficiency and levels of human comfort. This research project, covered in three papers, establishes the diffuser baseline performance and then determines the field installation adjustment values. The first paper covers baseline performance. This paper documents the field conditions difference in throw and pressure loss from ideal conditions of six types of ceiling diffusers, each with three different inlet sizes at three different inlet velocities. The third paper covers differences in sound generation from ideal conditions. Full scale laboratory testing of typical field installation variations was completed with variations in damper installation, duct approach angle, duct type, duct vertical height above the diffuser, and close coupling duct installation. A predictive model was developed and used to create a set of look-up tables that can be used to easily predict how the installation configuration would affect diffuser performance compared to published data. The results in this report can be used to determine the corrections for throw and pressure loss for field conditions from baseline results. [ABSTRACT FROM AUTHOR]

Building air distribution terminal system designers and system installers require accurate quantitative information on the noise performance of the installed system to achieve optimum system efficiency while maintaining preferred levels of human comfort. This research project, covered in three papers, establishes the diffuser baseline performance and then determines the field installation adjustment values. The first paper covers baseline performance. The second paper documents the field conditions difference in throw and pressure loss from ideal conditions of six types of ceiling diffusers, each with three different inlet sizes at three different inlet velocities. This paper documents the field conditions difference in sound performance from ideal conditions of the same variety of diffusers and inlet velocities. Full-scale laboratory testing of typical field installation variations was completed with variations in damper installation, duct approach angle, duct type, duct vertical height above the diffuser and close coupling duct installation. A predictive model for sound generation was developed and used to create a set of look-up tables that can be used to easily predict how the installation configuration would affect room sound levels compared to published data. [ABSTRACT FROM AUTHOR]

Thermally-Stratified Chilled Water (CHW) Thermal Energy Storage (TES) is a commonly used technology in large TES applications for peak load management of cooling or air-conditioning loads. However, CHW TES requires a large unit storage volume (proportional to the TES capacity and inversely proportional to the CHW supply-to-return temperature differential); also, the minimum operating supply temperature for thermally-stratified CHW TES is approximately 39 °F (4 °C), the temperature at which water exhibits its maximum density. This paper presents the use of an aqueous fluid (water with dissolved chemicals) as an alternative storage medium in thermally-stratified TES. Such Low Temperature Fluid (LTF) TES, compared to conventional CHW TES, can operate with a larger supply-to-return Delta T (for a smaller unit storage volume) and a colder operating supply temperature. The LTF TES technology has been employed commercially in a wide range of TES applications since 1994, in systems with individual TES capacities ranging from very small (60 ton-hrs or 210 kW-hrs) to very large (123,000 ton-hrs or 432,500 kW-hrs), and operating with supply temperatures ranging from 30 °F (-1 °C) to 38 °F (3 °C). The paper presents: * a discussion of the desirable characteristics of a LTF, * a description of the LTF chemistry, * thermo-physical properties of the LTF at various combinations of chemical concentration and temperature, * examples of operating installations, including end-user types, ages, capacities, and temperatures, * a representative example of thermal stratification operating data, * data related to the long-term chemical stability of the LTF, * data related to the long-term control, by the LTF, of corrosion and microbiological activity, and * a discussion of the comparative typical advantages and limitations of LTF TES versus those of the traditional technologies of CHW TES and ice TES. [ABSTRACT FROM AUTHOR]

This paper reviews the previous attempts to evaluate the Indoor Air Quality (IAQ), investigates previously proposed IAQ factors and analyses the evaluation methods of these factors. The present work introduces, also, a new hypothesis of the optimum HVAC airside system design of the surgical operating theatres to achieve the comfort and hygiene levels. The present work is devoted to propose and formulate a new scale capable of adequately evaluating the airflow pattern in the surgical operating theatres. The proposed new scale is proposed to cover the local and overall air quality evaluations. A new Neuro fuzzy technique was applied to derive measures for indoor air quality indices. Indoor Air Quality (IAQ) is more critical in healthcare facilities due to the dangerous microbial and chemical agents present and the increased susceptibility of the patients. Hospitals and other healthcare facilities are complex environments that require ventilation for comfort and to control hazardous emissions. Surgical operating theatre is the most important and complex zone in the hospital, and requires more careful control of the aseptic conditions of the environment. Most of the previous researches aiming at evaluating the IAQ were based on the evaluation of the air distribution depending on the residence and leaving age of the air supplied to the enclosure. Other attempts were also reported to indicate the effectiveness of contaminant removal by the entire airflow pattern as an indication to the IAQ. This paper recommends some designs of the supply air outlets to provide the vertically downward airflow as a practical solution. The near ceiling and near floor extract ports are to be used instead of the hypothetical complete floor extract as a practical solution. [ABSTRACT FROM AUTHOR]

The latest advances in HVAC technologies focus on delivering the exact cooling or heating required to each individual zone by modulating the system capacity. New technologies like variable speed compressors and inexpensive controls have allowed manufacturers to introduce a new family of direct expansion systems with multiple indoor conditioning coils. The HVAC design and modeling community is interested in analyzing reliable and accurate laboratory data on such systems to further understand the actual benefits. In a typical dual room psychrometric chamber used to test unitary systems, one chamber houses the outdoor unit and the other houses the indoor unit. The multi-split systems provide a unique testing challenge. With multiple indoor coils, a single indoor chamber is unable to simulate individual return air conditions to each indoor coil. This problem is further exacerbated in case of systems which can provide simultaneous heating and cooling. This paper details the design, construction, and commissioning of a novel multi-zone test facility (test stand) for multi-split heat pump systems. A four zone, 10-Ton (35.2kW) ducted test stand is constructed for testing multi-split systems. Each zone has individual temperature, humidity and air flow control which allows indoor coils to be tested at different conditions irrespective of the other coils. The temperature control is achieved by using resistance heaters and cooling coils while the humidity control is achieved by an air /water atomizing system. An axial fan upstream of the indoor units is used to deliver air flow with required static pressure. All three control systems - temperature, humidity and air flow - are controlled through a dedicated data acquisition system. The same system is used to collect data from various sensors. The paper elaborates on the design challenges, construction details and various instrumentation aspects of the test stand. [ABSTRACT FROM AUTHOR]

Heat pumps provide an efficient heating method; however they suffer from sever capacity and performance degradation at low ambient conditions. This has deterred market penetration in cold climates. There is a continuing effort to find an efficient air source cold climate heat pump that maintains acceptable capacity and performance at low ambient conditions. Systematic optimization techniques provide a reliable approach for the design of such systems. This paper presents a step-bystep approach for the design optimization of cold climate heat pumps. We first start by describing the optimization problem: objective function, constraints, and design space. Then we illustrate how to perform this design optimization using an open source publicly available optimization toolbox. The response of the heat pump design was evaluated using a validated component based vapor compression model. This model was treated as a black box model within the optimization framework. Optimum designs for different system configurations are presented. These optimum results were further analyzed to understand the performance tradeoff and selection criteria. The paper ends with a discussion on the use of systematic optimization for the cold climate heat pump design. [ABSTRACT FROM AUTHOR]

A huge barrier to wider adoption of building automation systems (BAS) in commercial buildings is their complex, time-consuming, and often proprietary installation, configuration, and commissioning process. A framework for plug-and-play HVAC air-handling unit (AHU) control systems is proposed in this study. This is the foundation and the first step toward a plug-and-play HVAC control system that will eventually lead to self-configuring HVAC control systems for automatic BAS setup, configuration, commissioning, and possible automatic detection and repair of potential controls problems. This framework is built on commercially available smart transducers that are compatible with the IEEE 1451 family of standards. To solve the critical issue of resolving system ambiguity, a structural pattern recognition algorithm is developed to automatically recognize temperature sensor locations in an AHU. The algorithm can be a critical part of a plug-and-play or self-configuring HVAC control system in establishing a binding list of control system input/output and automated assignment and verification of the binding list. This work consists of two parts. Part I, the present paper, reviews existing technologies and discusses technology gaps for incorporating plug-and-play and self-configuring concepts into HVAC control systems. A plug-and-play framework for an AHU is then proposed. Part II (Zhou and Nelson 2011), a companion paper, develops a structural pattern recognition algorithm to automatically identify AHU temperature sensor locations and a scheme to resolve AHU system ambiguity. A prototype of the plug-and-play framework for an AHU was built and tested in an experimental facility. Tests are conducted at various initial conditions, environmental temperatures, and chilled-water system configurations to demonstrate the feasibility of the framework and the robustness of the pattern recognition algorithm. [ABSTRACT FROM AUTHOR]

An unglazed transpired solar collector, sometimes called a solar wall or UTC, can be used to preheat ventilation air with incident solar energy. In this system a dark colored collector made of sheet metal absorbs solar energy, transfers it to outdoor air passing through its perforated surface, and supplies it to a building air handling system. This system offers energy savings with a simple, efficient, and reliable design. Minnesota State University, Mankato has undertaken a study of UTC installations in the Minneapolis-St. Paul region for the Minnesota Office of Energy Security. This study includes several different UTC installations; including a corporate building, a K-12 institution, and a public services building. In each case the UTCs and/or buildings have different characteristics from each other. This paper will begin with a brief background on UTCs and will then discuss typical climate conditions, determined through weather logging, and the resulting solar wall performance, determined from temperature and energy management system logging. The paper will conclude with a discussion of the suitability of unglazed transpired solar collectors for buildings in the Minnesota climate. [ABSTRACT FROM AUTHOR]

Liquid-to-air coils used as air heating system coils and air system cooling coils for air-conditioning, refrigeration etc. rarely use their design capacity. The capacity must therefore be reduced accordingly, traditionally by means of on-off operation or by means of control valves. Draw-backs of traditional control are excessive pressure drop and drive power to pumps due to high flows as well as the need for balancing valves and control valves with authority. There are, however, possibilities to substantially reduce the drive energy of pumps and fans for air coils, e.g. by replacing valve and damper control by direct control of decentralized pumps and fans. This may achieve better control at a lower cost while using substantially less drive energy. This paper includes basic analysis of heat transfer and control methods to study how coil design affects the transfer function of an air coil on capacity turn-down. The analysis indicates that direct flow control, using variable-speed pumps, may require only a fraction of the drive power needed by traditional valve control. Furthermore, system designs for low flow rate and pressure drop also provide opportunities for new types of laminar-flow coil designs. Results show that the transfer functions of alternative control methods for the capacity and outlet temperatures of air coils can be written as simple functions of the controlling variable (supply temperature, inlet temperature or coil liquid flow rate). The transfer functions may be tailored to specific needs by changing design parameters such as the design values of air and liquid flow rate and the heat transfer characteristics and heat transfer areas of the respective air and liquid sides. Also, the paper provides an example of alternative system design and control strategy. [ABSTRACT FROM AUTHOR]

This paper provides a new implementation model of the BACnet objects on high-level functionality for variable refrigerant flow (VRF) air-conditioning systems for commercial buildings. First, the paper discusses a model of the air-conditioner cell that consists of a group of BACnet standard type objects using the Unified Modeling Language (UML). In addition, this paper provides a new concept of a virtual wattmeter using the BACnet Accumulator object type for power consumption allocation to each tenant of the building. Examples of computer simulation and field testing show the effectiveness of our approach to expedite communication access and to provide more accurate allocation of power consumption for VRF air-conditioning systems. [ABSTRACT FROM AUTHOR]

Variable Air Volume (VAV) systems are commonly used to maintain space comfort in commercial buildings. Single-Duct VAV (SDVAV) systems often use Fan-Powered Terminal Units (FPTU) to control the amount of conditioned air that is delivered to a zone to maintain space conditions. A model was developed to evaluate the operation of a SDVAV system using Series and/or Fan Powered Terminal Units. The procedure used to model the system is described in this paper as are the equations used to model all non-zone level components in the system. The SDVAV system model was verified in the laboratory using a test stand that supported the operation of a three zone system using both series and parallel FPTU. The test stand was set up to mimic the operating points as predicted by the model. System operation was measured and then compared to the predicted values. The details of the model verification are described in another paper. [ABSTRACT FROM AUTHOR]

This paper presents a means to quantify air flow performance of both traditional raised floor designs and non-raised floor air-conditioning designs for data centers. Metrics are developed that will readily permit owners, engineers and operators to measure and quantify the effectiveness of their data center cooling systems or changes that they make to their cooling systems to increase air cooling efficiency. The metrics incorporate and integrate together the major factors that decrease the effectiveness of computer room air cooling. These factors, which are covered in the paper, include; negative pressure flow rate (air induced into the floor void), bypass flow rate (from floor void directly back to the air-conditioners without cooling servers), recirculation flow rate (from server outlet, back into server inlet) and the balance of CRAC and server design flow rates. Examples of the application of these metrics are also presented. [ABSTRACT FROM AUTHOR]

The air distribution systems in rooms can often be considered to be fully mixed, except for systems as e.g. displacement ventilation. The degree of the mixing process and its influence on passive smoking, cross infection risk, and other interaction between people in a room have already been studied with respect to macroscale. This paper discusses the flow in the microenvironment between people in rooms. It is shown that the flow around a person (the source) influences other persons in different ways. If the persons are standing at some distance, the general air distribution system in many cases creates a fully mixed concentration, which to some extent protects people from a high exposure from the source person. If people stand close to each other there may exist a direct flow from the source person to the other persons. The measurements shown in the paper are made by thermal manikins with tracer gas supplied to the breathing flow. The measurements show that the level of cross infection, or flow of tracer gas from one manikin to the other has two routes. One route is through the room air as background concentration, and the other is through a direct flow between two people because of the exhalation from the source manikin. This effect in the microenvironment is important when the distance between the persons is smaller than 1.2 m. The paper shows the effect in rooms with different air distribution systems. [ABSTRACT FROM AUTHOR]

This paper presents the design and heat transfer calculations of a new psychrometric environmental control climate chamber for heat pump and refrigeration systems testing. First, the standards for rating air conditioning and refrigeration systems are used to determine layout and floor area of the chamber. Then, a heat transfer model is developed to estimate the heat gain from the surrounding into the climate control chamber when the interior conditioned space is at temperature below freezing. The model, which was validated with data from the literature, also computes the wall thickness that would prevent water vapor condensation and subsequent accumulation on the outside walls of the facility. The results show that if the interior room temperature is below-20 °F (-28.9 °C), the thickness of the walls of the chamber ranges between 4 to 5 inches (10.2 to 12.7 cm), depending upon the thermal conductivity of the insulation panels. The outcomes of this paper also suggest that the cooling capacity of the conditioning system should be slightly oversized with respect to the capacity of the testing equipment inside the chamber. The additional capacity compensates for the heat transfer gained from the surrounding to the interior of the chamber, which is driven by the large temperature difference during testing at temperature below - 20°F (-28.9°C). [ABSTRACT FROM AUTHOR]

This paper reviews result of approximately fifteen months of monitoring of four houses located in the desert climate of Borrego Springs, California. Four houses were constructed using identical floor plans but differing wall materials, and different cooling systems that were designed to reduce energy use in this extreme hot climate. Cooling systems evaluated include a high SEER two-speed air conditioner, an evaporative condenser, two prototype two-stage evaporative coolers, and two floor cooling systems. Detailed monitoring was used to develop performance maps for the air conditioning systems which are compared to manufactures' data. Energy savings for the high performance systems was evaluated relative to a standard 13 SEER air conditioner, and the economic potential of these systems is reviewed. The paper also evaluates the performance of two unique floor cooling systems. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the current regulations, standards and guidelines relating to the ventilation and fire control systems provided in road tunnels in the United States and other countries. First, the paper discusses the three types of documents; regulations, standards and guidelines. This paper also provides a brief discussion of some of the more common ventilation and fire control systems as addressed in these documents. In addition, this paper presents lists of some such documents that exist on a global basis. [ABSTRACT FROM AUTHOR]

This paper addresses the field cooling performance of a natural gas-engine-driven heat pump (GHP) system for space cooling and heating applications. Performance data were collected from six 10-ton GHP units installed at six military installations in the southwest United States. Note that the test sites in the southwest United States offer challenging operating conditions to air-cooled space cooling systems. Theoretical analysis showed significantly higher energy efficiency in space heating and cooling by GHP units compared to a conventional gas furnace for heating and electric direct expansion (DX) system for space cooling. In this paper, field measured cooling performance of the GHP units was compared to the theoretical efficiency during the 3 months of the 2007 cooling season. An independent laboratory reported testing GHP system performance in a laboratory environment (Zaltash et al. 2007). The test results are presented in the same symposium session featuring GHP technology, and will be published in the same ASHRAE Transactions volume. GHP performance under field conditions and laboratory conditions were compared. This paper also presents the GHP system's energy conservation and cost savings potential in space air conditioning. [ABSTRACT FROM AUTHOR]

This paper is the first of three papers on the development of experimental performance models of variable air volume fan powered terminal units. Tests were conducted on both parallel and series fan powered terminal units. Data from these tests were used to develop empirical models of airflow, power, and leakage of both parallel and series fan power terminal units. These models are suitable for use in annual energy use models of variable air volume systems in commercial buildings. This paper provides a description of the experimental apparatus, the terminal units, and measurements for airflow and power. Both 8 in. (203 mm) and 12 in. (304 mm) primary air inlet terminal units from three manufacturers were evaluated. [ABSTRACT FROM AUTHOR]