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In order to obtain high power and efficiency while operating PEM fuel cells in airborne applications, pressurizing the inlet air is necessary. The control strategy for dynamic operation of an air supply module was developed in order to provide cathode inlet air at optimal conditions (mass flow, pressure, humidity and temperature) for different ambient conditions and varying power demand. A surge avoidance strategy without additional surge control valves was successfully implemented. The system was successfully tested statically and dynamically and afterwards connected to a fuel cell system. The air supply module was able to provide cathode pressure, mass flow and humidity dynamically as requested and the developed control strategy was able to avoid unstable operation. •Air supply system for pressurized hydrogen fuel cells in aviation was developed. •Control strategy for varying mass flow, pressure and power demand was developed. •Statically and dynamically stable operation over complete compressor map is achieved. •Measurement data from a combined system with a fuel cell stack is presented. [ABSTRACT FROM AUTHOR]

Active adjustment of the airflow organization in data centers (DC) has been increasingly applied due to its superior adjustment performance. But for now, the main focus is on the airflow distribution optimization in the horizontal direction, while few research has been conducted to investigate the additional energy consumption of active method. This paper introduced the jet-induced ventilation into under-floor air distribution (UFAD), then the coupling air supply system (CASS) was established. Taking the CASS data center as an example, this paper focuses on the impact of the active adjustment method on both airflow organization and energy consumption of the DC, and analyzes the energy consumption of the system while meeting the security operations of the thermal environment. The results showed that the incorporation of jet-induced ventilation effectively improved the airflow distribution uniformity, while the active adjustment of the airflow organization in the DC has little effect on the overall energy consumption. On the premise of meeting the demand of thermal environment, the energy consumption of the CRAC (Computer room air conditioning) units in the CASS is reduced and the change of the overall energy consumption is small, while the total energy consumption increased with the increase of airflow uniformity. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of approaches to ensuring the performance of a ramjet combustor using an unconventional method of measuring the thrust in testing an experimental model of a liquid-fuel combustor under flight conditions simulated by a fired heater. The thrust and drag of the combustor model were measured in firing tests with an attached air duct using a thrust meter. Thrust is a parameter that characterizes the energy potential of any engine. The conventional method of determining the thrust and economic characteristics of a heat engine involves lengthy multi-parameter studies and calculations of the operation performance. The new method allows one to detect the effect of any parameter or element of the structure on the physical process in a combustor in units of the developed thrust and evaluate the change in any parameter by the thrust level directly in firing tests. The proposed thrust measurement system makes it possible to refine the strategy of implementing the combustor operation at an early stage of testing, thus reducing the amount of intermediate calculations and saving a huge amount of time and money. This, combined with static pressure measurements along the combustor length, allows a guaranteed prediction of the direction of search for improving the operation performance. Ways are shown to improve the ramjet combustor performance using a thrust meter to evaluate the overall engine performance under conditions of limited technical and methodical possibilities in firing tests. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic control strategy of air-conditioning air supply volume based on statistical data of the spatial and temporal distribution of occupants in the building, aiming at reducing overheating in buildings under local heat island effect. Nowadays, energy consumption in air-conditioning system is relatively high when considering the limited number of occupants and chiller plants operating inefficiently because the traditional central air-conditioning system was not designed to operate at different cooling load demands. Therefore, variable air volume (VAV) air-conditioning system is applied in this paper with corresponding wind volume control method. To address the above issue, in this paper: (1) A spatiotemporal distribution of occupants in the building is analyzed, and the relationship between occupant distribution and characteristics of the thermal dissipating load is established; (2) A strategy for dynamic controlling of the air supply volume in time and space is proposed; (3) A distributed photovoltaic system supplies power to cooling load of the building, and a strategy is proposed for optimizing the match between cooling power and photovoltaic (PV) output power using competitive swarm optimization algorithm; and (4) Air blower total amount of wind control method is adopted in VAV air-conditioning system for dynamic controlling of the air supply volume. This paper uses a simulation to verify the feasibility and optimality of the above strategies. The simulation results show that the building energy consumption is greatly reduced by 39.52%, the PV accommodation is improved as 77.14%, and four control indicators are well satisfied due to the air blower total amount of wind control method. [ABSTRACT FROM AUTHOR]

The smoke layer height in the ship engine room under forced ventilation has been experimental and theoretical investigated in this work. A series of test were carried out in a scaled engine cabin experimental platform to obtain the influence of air supply volume and air inlet height on the burning parameters, including the mass loss rate, smoke temperature, etc. The research results show that under the experimental conditions, the fire source mass loss rate increases exponentially, and smoke layer height also increases gradually with the increase in the air supply volume. The empirical formula of smoke layer height under different air supply conditions was given. Then, a prediction model of smoke layer height under different forced ventilation conditions was constructed through theoretical analysis based on conservation equations. Within the range of experimental air volume and air inlet height, the relative error between theoretical prediction results and experimental results was less than 11%, which could effectively predict the smoke layer height in the ship cabin fire. [ABSTRACT FROM AUTHOR]

The traditional thermal environment management of the passenger compartment adopts the unified regulation method. Air distribution formed in this manner often causes thermal comfort and energy consumption problems. In view of the problems of conventional airflow organization, a new air supply strategy-variable air volume and temperature strategy is proposed. In this air supply strategy, variable air volume and variable temperature air supply is carried out according to the characteristics of thermal comfort requirements of passengers in different periods and positions in the cabin. STAR-CCM + software coupled with THESUES-FE software was implemented and compared with different air supply methods. The performance of the air supply strategy was evaluated based on PMV-PPD evaluation index. The results show that the variable air volume variable temperature air supply strategy has certain advantages and improves the thermal comfort level of the crew cabin. The cooling capacity of the automobile air conditioning is allocated effectively, thus improving the satisfaction of the occupants to the thermal environment. This strategy not only saves energy, but also improves the cooling effect in the cabin. [ABSTRACT FROM AUTHOR]

Personalized air conditioning systems are widely used in sleeping environments, where a sleeping human body is always immobile through night. The ventilation performance optimization of air conditioning system becomes necessary, and the influences from different supply air parameters were investigated in this study, including supply air flow rate and temperature, supply air outlet height and fresh air flow rate. To understand the effects of supply air parameters on ventilation performance, the occupied zone air flow field, air change efficiency, CO2 concentrations and CO2 concentrations distributions inside the room were numerically studied. It was indicated that placing the supply air outlet at lower levels of 1.1 and 0.8 m could directly deliver cooling air to the thermal manikin, leading to a much higher air change efficiency of around 70%. The air temperature of the occupied zone could not be well cooled down for the supply air outlet at a height of 0.8 m. Meanwhile, the higher supply air flow rate may cause significant draft risk. Finally, considering the ventilation performance and draft risk, a set of the supply parameters is suggested for this personalized air conditioning system. [ABSTRACT FROM AUTHOR]

• Two types of flames in a reduced-diameter vortex combustor were analyzed. • The two-layer flame with secondary combustion near the wall achieves higher fuel utilization. • The flame structure is the result of the combined effect of the central jet and cyclone vortex. • The cyclone vortex has a strengthening effect on the mixing of the fuel and secondary air. In this paper, the combustion process in a vortex combustor, which is composed of two volutes, a center nozzle, and a reduced-diameter cavity, is studied by CFD simulation. The combined effect of the center jet and cyclone vortex on the flame structure is revealed by analyzing the fuel transport mechanism and flow field characteristics. Results show that under different fuel and air supply conditions, two typical flame structures may form inside the combustor. When the equivalence ratio is 0.5 and the power is 40 kW and 50 kW, Flame A will be produced, which is mainly distributed near the center nozzle. Under other conditions, Flame B will be generated, which is a two-layer structure with an inner layer surrounding the center nozzle and an outer layer near the wall. The construction of Flame B inside the reduced diameter vortex combustor is mainly attributed to the strong cyclonic flow, which breaks the recirculation in the flow field, transporting the fuel to the near wall region and promoting secondary combustion. At this time, the methane burn rate can be as high as 99 %, which is 10 % higher than the methane burn rate of Flame A. [ABSTRACT FROM AUTHOR]

Modeling of the aerodynamic processes involved in the ventilation of a large production enclosure containing electrical equipment requiring special conditions for air humidity and temperature was performed. A physical-mathematical model of the aerodynamics of ventilation of a production enclosure is presented, taking into account heat exchange with air and the surface of the equipment present in a building and mass exchange with the ambient environment by air filtration through the structural elements. The computational results for non-stationary displacement of air with high humidity from the building by means of ventilation with dried air are presented. The characteristic time of purification of air from excess moisture with air supplied to various parts of a building was determined. [ABSTRACT FROM AUTHOR]

• The cabin heat dissipation was analyzed under two ventilation modes (air supply/air exhaust). • The Experimental devices and CFD method were introduced and the results comparison were made. • The flow fields of the two conditions were analyzed and compared. • A better heat dissipation environment of reefer container was obtained in the air supply condition. In global refrigerated transportation, marine reefers play an extremely important role. Considering the high freight cost and harsh surroundings of the decks during the voyage, reefer containers are always loaded into cabins for safe and economical purpose. However, under severe environment conditions in cabin , the refrigeration efficiency of reefer units was greatly affected, because of the weak ventilation and low heat exchange capacity. In order to find a more scientific and reasonable way to ventilate the cabin of reefer containers, two different ventilation modes, that is, air supply and air exhaust, were experimented and simulated. The temperature distribution was analyzed in a typical reefer cabin with 14.4 m (in length) × 23.2 m (in width) × 16.85 m (in height). Compared with two contrary ventilation modes, the temperature distribution in the cabin at steady state was simulated and analyzed. The results show that, the temperature of the cabin under the air exhaust condition was about 4K lower than that under the air supply condition. But with higher heat dissipation efficiency, the air exhaust condition sacrifices the uniformity of the temperature in the cabin. A relatively uniform temperature distribution and airflow field were obtained under air supply condition. Therefore, considering the heat dissipation effect of the container and the uniformity of airflow distribution, the air supply method was recommended. The two ventilation modes were compared in detail in this paper, and the results provide a reference for ventilation design of reefer container vessels. [ABSTRACT FROM AUTHOR]

An experiment has been carried out for examining the performance of an air conditioning unit under constant outdoor wet-bulb temperature and varied dry-bulb temperature. During the experiment, the wet-bulb temperature of the compartment for outdoor unit was maintained at 22 °C and the dry-bulb temperature was varied from 24°C to 36°C. The increase of outdoor air temperature results in the increase of supply air temperature, discharge temperature, suction temperature, and liquid line temperature. These cause the degradation of the air conditioner performance. An increase of power consumption by 1.4% and decrease of cooling capacity by 0.8% were observed for each 1°C increase of outdoor air temperature. As a result, the energy efficiency ratio drops by 2% for each 1°C increase of outdoor air temperature. [ABSTRACT FROM AUTHOR]

Background: Airline crew members report adverse health effects during and after inhalation exposure to engine oil fumes sourced to the air supply system onboard commercial and military aircraft. Most investigations into the causal factors of their reported symptoms focus on specific chemical contaminants in the fumes. The adverse health effects reported in aircrew exposed to the aircraft air supply, bled unfiltered off the engine or Auxiliary Power Unit (APU) may be related to particulate exposures, which are widely known to effect health. While oil contaminates the aircraft air supply, some suggest that this will only occur when there is a bearing seal failure, others document that there is low level oil contamination of the air supply during normal engine operation. This brief pilot study explores whether particulate exposure may be associated with the normal engine/APU and air supply operation and to therefore increase the understanding that UFP exposures may have on crew and passengers.Methods: An ultrafine particle counter was utilised by an experienced airline captain in the passenger cabin of four short-haul commercial passenger aircraft. All flights were under 90 min on aircraft from two different carriers ranging from 7 months to 14 years old.Results: UFP concentrations showed maximum concentrations ranging from 31,300 to 97,800 particles/cm3 when APU was selected on as a source of air on the ground and with engine bleed air and the air conditioning packs selected on during the climb. In 2 of the 4 flights the peaks were associated with an engine oil smell. Increases in UFP particle concentrations occurred with changes in engine/APU power and air supply configuration changes.Conclusions: This study identified increases in UFP concentrations associated with engine and APU power changes and changes in air supply configuration. These results correlated with times when engine and APU oil seals are known to be less effective, enabling oil leakage to occur. The concentrations reached in the passenger cabins exceeded those taken in other ground-based environments. UFP exposures in aircraft cabins during normal flight indicates there will be health consequences for long serving aircrew and some passengers. [ABSTRACT FROM AUTHOR]

Trains are an important means of transportation for people to travel. The train's soft sleeper compartment space is relatively small, and the density of people is relatively large. Therefore, improving the thermal comfort and air quality of the compartment is of great significance for ensuring a healthy travel environment. To analyze the appropriate mode of conditioned air supply in train soft sleeper compartments, the airflow distribution inside soft sleeper compartments is simulated numerically at four different air supply modes, namely, sidewall air supply with slot diffusers, perforated ceiling air supply, bedside task–ambient air conditioning, and displacement ventilation. The reliability of the numerical simulation models is verified with the experimental data in the literature. Comparative analysis is made in terms of the compartment temperature, velocity, predicted mean vote and predicted percentage dissatisfied (PMV-PPD), and ventilation efficiency among various modes of air supply. The four air supply schemes are evaluated comprehensively by stochastic multicriteria acceptability analysis (SMAA-2). As the computational results show, bedside task–ambient air conditioning is the best air supply mode in terms of comprehensive performance indicators, followed by the sidewall slot air supply. The perforated ceiling air supply ranks third, and is superior to displacement ventilation. [ABSTRACT FROM AUTHOR]

Air well system of the Burgtheater Vienna: sustainable cooling strategies The Burgtheater Vienna was built at the end of the 19th century and it is one of the most important straight theatres in Europe. It is equipped with an air well system for the fresh air supply and conditioning of the auditorium. The air is drawn in at the Volksgarten nearby and led to the auditorium via an underground tunnel. Warm and used air is dissipated through the ceiling and the roof of the theatre. The original dimensions of the facilities are still apparent. In the framework of this study, temperature, humidity and air velocity sensors were positioned at significant places along the ventilation system and the data was evaluated over the summer 2019. As a result, optimization potentials regarding operation control and air cooling using water atomization were evaluated. Finally, it was shown that the air well system can be used to sustainably condition the theatre in a time of rising temperatures. [ABSTRACT FROM AUTHOR]

Demanding for quick-frozen food and its quality in modern life, the requirements for food quick-freezing technology become challenging.The impingement quick-freezing equipment has drawn much attention in the most advanced quick-freezing technologies.The appropriate low-temperature flow field in the heat exchange zone of impingement quick freezing equipment can reduce the time of food quick-freezing, while improve the quality of quick-frozen food. This paper aims to investigate the effect of air supply velocity on the freezing process of a single shrimp at the up and down within the chamber of impingement quick freezing equipment, using the numerical simulation and experimental verification. A single shrimp was selected as the research object. The main purpose of this research was to find the air supply conditions, which can shorten the freezing time of shrimp, and achieve the optimal flow field in the heat transfer area of the equipment. Three experimental groups were divided into: 1) the air supply velocity at the upper and downsides were kept the same and changed at the same time, 2) the air supply velocity of the upside was 15 m/s, while the downside was from zero to 15 m/s, and 3) the air supply velocity on the downside was 15 m/s, while that on the upside was from zero to 15 m/s. The results showed that the freezing time of the shrimp shortened, but the gradient of decrease also reduced, as the increase of air supply velocity, when the air supply velocity was the same on both sides of the up and down impingement quick-freezing equipment. When the air supply velocity on the upside was 15 m/s and the air supply velocity on the downside was from zero to four m/s, the relative impact of the two impinging jets can form an eddy current on the low velocity side, to promote the flow field on the surface of shrimp, and improve the heat transfer efficiency of shrimp. When the air supply velocity of the downside exceeds 4 m/s, the relative impact of the two impinging jets can form a jet vacuum zone with down velocity on the surface of shrimp, reduced the heat transfer efficiency of shrimp. With the continuous increase of the downside air supply velocity, this adverse effect first increased and then decreased, the maximum appeared when the upside air supply velocity was 15 m/s and the downside air supply velocity was eight m/s, and the frozen time of shrimp was the longest, which was 909 seconds. By the same token, when the downside air supply velocity was 15 m/s and the upside air supply velocity was from zero to two m/s, the relative impact of the two impinging jets can form an eddy current on the low velocity side, improve the heat transfer efficiency of shrimp. When the air supply velocity of the upside exceeded two m/s, the relative impact of the two impinging jets can form a jet vacuum zone with down velocity on the surface of shrimp, reduced the heat transfer efficiency of shrimp. With the continuous increase of the upside air supply velocity, this adverse effect first increased and then decreased, it had a maximum when the downside air supply velocity was 15 m/s and the upside air supply velocity was 5 m/s, and the frozen time of shrimp was the longest, which was 920 seconds. In the experimental range of impinging jet velocity, when the air supply velocity at the upside was 15 m/s and the air velocity of the downside was 2 m/s, the freezing time of shrimp was the shortest, which was 617 seconds. It infered that the influence of the upper impinging jet on the freezing process was greater than that of the down impinging jet on the freezing process in the upper and down impingement quick-freezing equipment. Therefore, the upper impinging jet can play a leading role in the impingement quick-freezing equipment.The finding can provide an insightful reference to design the promising operating conditions for the up and down impingement quick-freezing equipment. [ABSTRACT FROM AUTHOR]

Highlights • The bottom-supply mode and side-supply mode were studied contrastively. • The simulation results were validated by the physical experiment in the laboratory. • The indoor thermal environment, PPD and energy utilization efficiency were explored. • The bottom-supply mode provided better thermal comfort and lower energy saving. Abstract The growing energy consumption and thermal comfort of an air-conditioned room have attracted increasing public attention. As such, the performance of air-conditioning systems with two air supply modes for a simplified office room was studied by numerical simulation and physical experiment. An experimental investigation was developed in an environmental chamber to validate the simulation model. Numerical investigation was carried out subsequently for an office setting by the validated CFD model. The indoor thermal environment, human thermal comfort and energy utilization efficiency of two air supply modes were analyzed and compared in this study. The results showed that under both air supply modes, thermal stratification occurred in the model room, and the air flow velocity in the occupied zone was low. In addition, the results indicated that under 21 °C supply temperature, the air-conditioning system with bottom-supply mode provided better indoor thermal comfort of the occupied zone, but the energy consumption was higher than the side-supply mode. [ABSTRACT FROM AUTHOR]

The cooling time of mango boxes (initial temperature 19 °C) at different positions in a Unit Load Device (ULD) located in a test room of 6 °C was monitored. Plaster mangoes were used due to the high perishability of real mangoes. The influence of box designs (closed and top-open) on the cooling time were studied. Both box designs showed shorter Half-cooling time (HCT) at the bottom than at the top. Closed boxes exhibited more uniform temperatures in the ULD. Heat transfer in closed boxes was primarily conduction, while natural convection played a significant role in top-open boxes. Then, the ULD was exposed to variable ambient temperatures to simulate real conditions in an air cargo supply chain. The results demonstrate that the critical step is the airport tarmac; after 2 h for example, the temperature at the top rose to 50 °C (with external air at 32 °C), resulting in a 10 °C increase in the mangoes in the top box. • Box design is a determining factor of temperature uniformity in a unit load device. • Natural convection was found to be significant for the top-open box design. • Unit load device exhibits temperature stratification: high at top, low at bottom. • Daytime on tarmac for 2 h leads to a rise of 10 °C in product temperature. [ABSTRACT FROM AUTHOR]

• The system is applied to buildings with high moisture load. • Two-stage air dehumidification is adopted to distribute moisture load. • Seven operating modes are designed to match various environmental conditions. • Energy efficiency increases 3.19%-10.57% by regenerated air heating. • The better system performance could be obtained at low ambient air enthalpy. With the higher demand for indoor thermal comfort and the accurate control of air temperature and humidity, energy consumption in air conditioning systems is increasing over these years, especially for buildings with high moisture load such as natatoriums. However, freezing dehumidification is still widely adopted in eliminating moisture load, which requires lower evaporating temperature and causes excessive energy consumption. To improve energy utilization and efficiency, a heat pump-driven liquid desiccant dehumidification system is proposed in this research, the surface condenser and liquid desiccant dehumidifier are adopted to realize two-stage air dehumidification. In the summer condition, the solution in regenerator is heated by the condenser of heat pump and the residual heat is to heat the regenerated air, and the cooling capacity of heat pump is applied to the surface condenser and terminal heat exchanger, simultaneously the solution in dehumidifier is cooled by cooling tower. Under the meteorological conditions in Nanjing, the coefficient of performance could reach 6.148 in this proposed system, and compared to conventional air source heat pump dehumidification air conditioning system, the rising ratio of energy efficiency is between 11.4% and 80.7%. Eight cities in China are selected to analyze the energy-saving effects, and energy consumption could be reduced by 31.9%-63.2%, the result demonstrates the superior energy-saving potential and application prospect of the heat pump-driven liquid desiccant dehumidification system. [ABSTRACT FROM AUTHOR]

The Dynamic Pressure Regain Method, a new design method for uniform air supply, was proposed in this paper, based on the principle of total pressure balance. It can achieve uniform air supply by keeping equal dynamic pressure in adjacent sections of the main duct that opens up a new field for the design of uniform air supply duct system. Research was carried out through numerical simulation and full-scale experiment. First, the design steps of this method were proposed according to the flow characteristics in the duct. Then the recommended range of air velocity ratio was determined by numerical simulation calculation, and the resistance calculation formulas of the duct under this method were fitted. Finally, the full-scale experiment was carried out for the working conditions of inlet air velocity of 4 m/s and 5 m/s to verify the results of numerical simulation, including the total pressure balance, the uniformity of air supply system, the resistance calculation formulas of duct and the verticality of outlet airflow. The results showed that with a constant air velocity of the main duct sections, the variation of the total pressure loss was within 5 %, thus satisfying the total pressure balance; With a 0.6–1.0 air velocity ratio of the branch to main duct, the air volume imbalance rate of the branch duct was lower than 10 %; The error of local resistance calculation formulas of the duct system was no more than 3 %. The airflow deflection angle travelling out along the branch duct walls was within 20°. This complete design method of uniform air supply satisfies the total pressure balance and features simplicity, which decreases the air volume imbalance rate by 84 % compared with the static pressure regain method. Besides, when the size of the inlet duct remains constant, that of the design model will not change with the inlet air velocity. In addition, this study proposed the resistance calculation formulas that conform to the characteristics of its design model. [ABSTRACT FROM AUTHOR]

• A photovoltaic curtain wall coupled with an air-conditioning system is designed. • Curtain wall cooling and supply air reheating are achieved using heat recovery. • System performance is evaluated, taking an office in hot-humid summer as a case. • The system increases power output by 1.07% and achieves 27.51% energy savings. • Properly increasing channel thickness and photovoltaic coverage optimizes design. To address the problems of PV facade overheating and air-conditioning cold-heat offset, this study proposed a novel PV double-glazing ventilated curtain wall system (PV-DVF) that combined PV cooling and dew-point air reheating. A case study was conducted based on an office building with a south-facing PV-DVF in Hefei, compared to one with a conventional PV double-glazing insulated curtain wall system (PV-DIF). This study mainly includes mathematical modeling and validation, performance prediction, and parametric analysis. During a typical summer week, the results reveal that the PV-DVF system achieved (1) a 4.64 °C drop in PV temperature and a 3.4 W (1.07 %) increase in power output, with 7.10 % electrical efficiency; (2) a 2083.22 W reduction in cooling energy consumption; (3) a 4431.81 W reduction in reheat energy; and (4) total electricity savings of 27.92 kWh/day. In the summer, the total electricity savings reached 1566.33 kWh, with an energy-saving ratio of 27.51 %. Furthermore, parametric study results show that properly increasing channel thickness and PV coverage ratio achieves better energy-efficient performance. [ABSTRACT FROM AUTHOR]

Modern agricultural production puts forward higher requirement for environmental control. Uniform air distribution can form the stable temperature, humidity and velocity of indoor air, which is particularly important for agricultural production. In this paper, theoretical research is conducted on a nursery piggery and the velocity uniformity is defined to evaluate the performance of perforated ceiling ventilation. A new optimization method for airflow organization is developed, which improves the airflow organization based on the suitable air supply angle. It shows that the velocity uniformity is increased and then decreased with the increase of air supply angle, and the best air supply angle is around 35°. The optimal air supply angle changes with the plenum height, and there is a threshold for the plenum height. The best velocity uniformity can be achieved when the height of plenum is 0.5 m. Besides, the air supply velocity has almost no effect on the velocity uniformity. The optimization model for airflow organization based on the air supply angle is established and its accuracy is verified. Finally, a specific case is selected to compare and analyze the air distribution under different air supply methods, which verifies the feasibility of the optimization method proposed in this paper. • Velocity uniformity is defined to evaluate the performance of perforated ceiling ventilation. • A new airflow optimization method based on suitable air supply angle is developed. • The airflow organization optimization method is established and verified. • The best air supply angle is around 35°. • A specific case is selected to verify the feasibility of the optimization method. [ABSTRACT FROM AUTHOR]

It was revealed in a previous related study that for an air conditioning (A/C) system used in a sleeping environment, the height of its supply air outlet would significantly affect its ventilation performance in terms of effectiveness. To further examine the underlying reasons of the differences in ventilation performance, the air flow field, distributions of mean age of air, air change efficiency and distributions of CO 2 concentrations inside an experimental bedroom were numerically studied using CFD method under five different settings, where its supply air outlet was positioned at 5 different heights. The study results suggested that positing a supply air outlet at a lower level was effective in both saving energy and removing the exhaled CO 2 in a breathing zone, and when a supply outlet was positioned at a higher level, less CO 2 was removed from the region near the mouth of a sleeper. [ABSTRACT FROM AUTHOR]

Studies on the thermal environment of the electronic radar shelter have been mainly focused on the simulation of the unmanned thermal environment, and there have been few studies on experiments in the thermal environment. Additionally, a comparative study of the experimental results from manned and unmanned shelters has been missing. In this paper, we experimented in thermal environments of manned/unmanned shelter under different air supply conditions. The experiment was divided into cooled, ventilated, and heated trials analyzing three aspects: (1) The average temperature distributions of walls, air inlet points, air outlet points, and surfaces were measured over time under different conditions in an unmanned shelter. The temperature distribution curve was fitted into the function. (2) Based on different working conditions, the temperature distribution experiments were carried out in three different areas for subjects wearing short or long clothing respectively. (3) The wind speed was measured at each measuring point in the air supply pipeline under different working conditions. The wind speed distribution was detected on the setting surfaces. The experimental results show that: (1) The air does not gradually tend to steady state with the time, and under different conditions, the air temperature obviously differs. (2) The clothing selection, air supply conditions, and locations of measuring points have significant influences on human body temperature distribution and left–right difference. (3) The mixing of the thermal plume caused by the vertical temperature difference of the human body and the jet generated by the mechanical air supply will reduce the wind speed of the airflow in the cabin, the adsorption of the jet to the bulkhead, and the stability of the airflow. The experimental data can provide the initial and boundary conditions for the simulation of the shelter. The results can provide a reference for the study of fluid control methods, the setting of thermal boundary conditions, and the simulation of the influence of thermal plumes on the airflow distribution. The experimental study in this paper has filled in the blanks regarding experimental study in electronic radar shelters. It has important research value and practical significance. [ABSTRACT FROM AUTHOR]

A computational fluid dynamics (CFD) numerical simulation method was used in this study to simulate the indoor thermal environment affected by three air-supply modes, upper-supply bottom-return mode, upper-supply top-return mode, and bottom-supply top-return mode, in the condition of the fixed point heat source, and explored the change rule of the predicted percentage dissatisfied (PPD) affected by the three air-supply modes. A suitable air-conditioning supply mode might better meet the requirements of human to the indoor thermal environment. The results, based on the calculation and analysis of indoor air distribution, temperature field, and thermal comfort, showed that the mixing degree of supply air and indoor air of upper-supply mode was better than that of bottom-supply mode, and the uniformity of temperature distribution of upper-supply top-return pattern was better. Moreover, in the personal breathing zone (0.8–1.6  m), the pattern of upper-supply top-return obtained the lowest PPD value. It can be seen that the mode of upper-supply top-return is more comfortable according to the evaluation index of human thermal comfort. [ABSTRACT FROM AUTHOR]

Highlights: [•] The key issue for efficient performance of UFAD system is to ensure the thermal stratification establishment. [•] The unnecessarily excess air supplied to the room deteriorates the thermal stratification. [•] Improper UFAD operation increases the fan power and HVAC electric demand. [•] The proper UFAD system is typically more efficient than the existed UFAD system with energy savings of about 23–37%. [•] UFAD system shows over the CBAD system saving by about 37–39% during the peak months and 51% during October. [ABSTRACT FROM AUTHOR]

This article reports on the continued study of the thermal environment in indoor spaces with under-floor air distribution systems, with a focus on the determination of supply airflow rate. Supply airflow rate of under-floor air distribution needs to be carefully determined to achieve thermally comfortable conditions in an occupied space. The design parameters, such as airflow rate, temperature of supply air, and types and number of diffusers, need to be properly calculated to ensure an acceptable vertical temperature difference between the head and ankle of occupants. This study introduced an empirical model to predict the vertical temperature difference between the head and ankle of occupants and calculated the supply airflow rate for under-floor air distribution design. This investigation developed the model based on a database summarizing vertical temperature distributions that correspond to various airflow and thermal conditions. The model used dimensionless numbers to group design parameters in order to represent the two driving factors of thermal stratification, namely, inertial and buoyance forces. Linear regression analysis was conducted to correlate the empirical equations of stratification for swirl, square, and linear diffusers. With the model, this study developed an airflow calculation method for under-floor air distribution as well as a graphical interface for designers. [ABSTRACT FROM PUBLISHER]

A vertical temperature gradient is known to occur in an enclosure that is ventilated by stratified air distribution (STRAD) methods. Thermal stratification offers distinct energy-saving possibilities. For example, a portion of heat gains can be excluded when calculating the air supply rate and the air-conditioning load. The cooling load reduction of a heat source depends primarily on its vertical location and radiant and convective split. In this study, an effective cooling load factor (ECLF) was defined to calculate the effective heat gains, which can be used by design engineers for the determination of the reduced-supply airflow rate and reduced cooling coil loads for common- and split-return/exhaust configurations with STRAD. Numerical simulations used to obtain these factors for various internal heat sources in a small office were presented, and on-site measurements were carried out to validate the performance of computational fluid dynamics in predicting the thermal stratification in large spaces. A fully developed database of ECLFs will be very useful when designing such systems. [ABSTRACT FROM AUTHOR]

Two independent field intervention experiments were carried out in mechanically ventilated classrooms receiving 100% outdoor air. Outdoor air supply rate and filter condition were manipulated to modify indoor air quality, and the performance of schoolwork was measured. The conditions were established for one week at a time in a blind crossover design with repeated measures on 10- to 12-year-old children in two classes. Seven exercises exemplifying different aspects of schoolwork (numerical or language-based) were performed as part of normal lessons by pupils who also marked visual analogue scales to indicate their environmental perceptions and the intensity of any symptoms. The children indicated that the air was fresher but otherwise perceived little difference when the outdoor air supply rate increased from 3.0 to 8.5 L/s (6.4–18 cfm) per person, while the speed at which they performed two numerical and two language-based tasks improved significantly. A significant effect of ventilation rate was observed in 70% of all the statistical tests for an effect on work rate, but there were no significant effects on errors. The effects were probably due to improved air quality in the classrooms as judged by a sensory panel of adults blind to conditions, as perceived by children, and as indicated by the reduction in the average CO2 concentration from 1300 to 900 ppm, taking this as a marker of reduced bioeffluent concentration. It was not possible to test the effect of replacing a soiled filter with a new one because very little dust had been retained by the ‘used’ filter and because of an incompletely balanced design. The unbalanced design also made it impossible to test for an interaction between filter condition and ventilation rate. These results indicate the importance of improving indoor air quality and ventilation in classrooms. [ABSTRACT FROM AUTHOR]

The present study evaluates the potential upgrade of a Linear Fresnel Reflector (LFR) collector at the Cyprus Institute (CyI) with photovoltaics via the calculation of the Levelized Cost Of Heat (LCOH). For over 4 years the collector has been supplying heating and cooling to the Novel Technologies Laboratory (NTL) of the Cyprus Institute (CyI). Extensive measurements have been carried out both on the LFR and NTL to render real numbers in the computations. This hybridization would be undertaken with the installation of PV arrays under mirrors, so that the collector is able to either reflect direct radiation to the receiver to process heat or to produce electricity directly in the built environment. The main objective is the decrease of the LCOH of Linear Fresnel collectors, which hinders their wider deployment, while air conditioning demand is globally booming. The results show that the LCOH for a small LFR to supply air conditioning is high, c€25.2–30.1 per kWh, while the innovative PV hybridization proposed here decreases it. The value of the study resides in the real data collected in terms of thermal efficiency, operation, and maintenance. [ABSTRACT FROM AUTHOR]

This study investigated the annual energy saving potential and system performance of two different evaporative cooling-based liquid desiccant and evaporative cooling-assisted air conditioning systems. One system used an indirect and direct evaporative cooler with a two-stage package to match the target supply air point. The other was equipped with a single-stage, packaged dew-point evaporative cooler that used a portion of the process air, which had been dehumidified in advance. Systems installed with the two evaporative coolers were compared to determine which one was more energy efficient and which one could provide better thermal comfort for building occupants in a given climate zone, using detailed simulation data. The detailed energy consumption data of these two systems were estimated using an engineering equation solver with each component model. The results showed that the liquid desiccant and dew-point evaporative-cooler-assisted 100% outdoor air system (LDEOAS) resulted in approximately 34% more annual primary energy consumption than that of the liquid desiccant and the indirect and direct evaporative-cooler-assisted 100% outdoor air system (LDIDECOAS). However, the LDEOAS could provide drier and cooler supply air, compared with the LDIDECOAS. In conclusion, LDIDECOAS has a higher energy saving potential than LDEOAS, with an acceptable level of thermal comfort. [ABSTRACT FROM AUTHOR]

The Protector XStream Hood incorporates a patented design and technology that differs from any other safety ventilation system. Exclusive features include the curved air foil with innovative Clean-Sweep openings, creating a constant, protective barrier from contaminants. The slotted baffle directs in-flow air from the hood face to the baffle in the non-turbulent laminar streams. A secondary baffle counteracts upward air streams that create airflow "roll" in traditional hoods. The Upper Dilution Air Supply and perforated slash handle design enhance user protection and containment by introducing fresh air near the user's breathing zone and reducing chemical fume concentrations.