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Manufactures of fin-and-tube heat exchangers often employ predictive modelling tools in order to reduce development cost and time. These tools require high-fidelity experimental data to validate the accuracy of their predictions. To that end, this paper presents the design and development of a custom-designed pumped refrigerant loop to collect high-fidelity experimental data for fin-and-tube heat exchangers in three operating modes: (1) single-phase refrigerant, (2) evaporator, and (3) condenser mode. It is combined with a small-scale wind tunnel installed in a psychrometric chamber facility for the purpose of validating the recently developed discretized fin-and-tube heat exchanger models (Sarfraz et al., 2019a and 2019b). The pumped refrigerant loop is able to precisely control desired refrigerant test conditions, flowrate to each individual heat exchanger circuit, and has been sized in order to test heat exchanger coils up to a capacity of 5 tons (17.5 kW). A preliminary test plan and uncertainty analysis is presented for the first heat exchanger coil to be tested. The uncertainty analysis showed that the experiment will have the capability of measuring overall coil capacity within ±2%. A design of experiments is also presented, which suggests that 9 tests per coil is an adequate number for minimizing experimental effort. A preliminary experiment was performed which showed that the average air and refrigerant side capacities match to within 1.1% of each other. This provides evidence that the experimental setup has the capability to far exceed the 5% threshold set by ASHRAE Standard 33 (2016).

Plug loads are one of the main contributors to the overall energy consumption in most office buildings. The plug and miscellaneous loads account up to 50% of the energy consumption in buildings (NBI, 2012). ASHRAE Fundamentals handbook (2017) provides power consumption data for various office equipment and load factor data for various office spaces. Load factors for different office types in the 2017 ASHRAE Fundamentals Handbook are conservative values based on equipment peak power consumption and diversity factor values. The individual equipment diversity factor provided in the Handbook is used to calculate the load factors. However, no data is provided for the office level diversity containing a mix of different equipment. For this paper, power consumption data is collected over three-week period for an office suite containing four different office spaces, each with a different mix of equipment. Load factors are calculated for the office spaces based on the equipment peak power consumption and using the individual, combined equipment, and office level diversity factors. The load factors calculated based on combined equipment diversity factors are compared with those based on individual equipment diversity factors. The calculated load factors are also compared against the load factors provided in 2017 ASHRAE Fundamentals Handbook. References: ASHRAE. 2017. Handbook of Fundamentals. American Society of Heating, Refrigerating, and Air Conditioning Engineering, Inc. Atlanta: ASHRAE. New Buildings Institute (NBI). 2012. Plug load best practices guide: Managing your office equipment plug load. https://newbuildings.org/resource/plug-load-best-practices-guide/ (accessed 12/04/2017)

Vapor compression systems are the most widely used system type in heating, ventilation, air-conditioning, and refrigeration (HVAC&R) applications. Experimental and numerical modeling techniques are used to analyze the performance of the vapor compression systems. With the introduction of high-performance computers, numerical modeling techniques are used extensively to develop cost-effective and efficient HVAC&R equipment. Experimental iterations on the design of vapor compression systems are costly; however, numerical techniques can reduce the number of experimental iterations, substantially decreasing the development cost and time. Because of the benefits associated with the numerical simulation, many researchers working in the HVAC&R field have attempted to develop efficient, robust, and accurate simulation models. This paper provides an in-depth review of heat exchanger modeling techniques as well as integration strategies to develop holistic system models.

Dedicated outdoor air systems (DOAS) make use of the sensible and latent capacity of the return (exhaust) air to cool and dehumidify the supply (outside) air. “Closed DAOS” is an advanced form of typical DOAS with desuperheater and evaporatively cooled condenser in the return air stream. The air entering the condenser in Closed DOAS is in the fully saturated state. In order to fully saturate the return air, it needs to be sprayed by water. Sufficient amounts of water is required for fully saturating the air and keeping the coils of the condenser wet during the process. This water is obtained internally as a result of condensation on the evaporator fins, not requiring additional water use at the buildings site. Closed packaged configuration requires to have a water balance of water obtained in evaporator to that required for saturating the air and wetting the condenser coil. This water balance can be achieved under most conditions by an optimal control of enthalpy wheel and heat wheel (run around heat exchanger) effectiveness to control the amount of water obtained in the evaporator. The optimal control of heat and enthalpy wheel effectiveness is not only important for making the necessary water balance but also to keep the latent load as low as possible. This paper discusses the Closed DAOS configuration with psychrometrics and water balance analyses.

A wind tunnel conditions the air flow for testing equipment, such as heat exchangers, over a wide range of conditions. In this paper, a procedure to develop the operating envelope for the tested equipment in a wind tunnel is presented. The temperature and humidity of the air that requires conditioning is controlled and maintained by the combination of cooling coil (or evaporator), heating elements, and a steam injection system. Therefore, the capacity of the components to be tested inside the wind tunnel is limited by the combined capacity of the cooling coil, heaters, and the steam injection system. For cooling coils or evaporators, an analysis is performed for different sensible heat ratios (SHR), inlet temperatures, and humidity. A similar analysis is performed for sensible heating coils or condensers where the SHR is 1. Â For a cooling coil or evaporator of a capacity of more than 3 tons, the condition of air inside the wind tunnel can be controlled by heating elements and steam injection system. Low capacity cooling and sensible heating equipment may require operation of the cooling coil, heating elements, and steam injection depending on the required temperature and humidity in the tunnel. The psychrometric and thermodynamic analysis for determining the operating envelope is performed for both heating and cooling equipment using ACHP (Bell , 2010). Heat transfer between the wind tunnel and its surroundings is calculated using a simplified heat transfer model adopted from literature (Cremaschi & Lee, 2008).

This paper provides a review on the fouling mechanism and its effect onto the performance of finned tube heat exchangers in HVAC systems. Fouling tends to degrade the performance of heat exchangers by decreasing the heat transfer coefficient and increasing the air-side pressure drop across the heat exchangers. Air side fouling depends on a number of factors on the air side, including type and concentration of fouling matter, size of particles in the fouling matter, and air velocity. Additionally, it depends on the heat exchanger design, e.g. heat exchanger geometry, fin geometry, and fin spacing. Various studies indicate that the effect of fouling on air pressure drop is higher than its degrading effect on heat transfer coefficient. Studies on heat exchanger fouling in HVAC systems indicate that the actual effect of the fouling onto system efficiency additionally depends on the employed refrigerant.Â