Evaluation of environmental and physiological factors of a whole ceiling-type air conditioner using a salivary biomarker

In order to improve environmental condition such as humidity and airflow in living spaces, a whole ceiling-type air conditioner is proposed. This novel air conditioner exhaust dispersed airflow from the whole ceiling by using a 3-dimensional knit fabric. The purpose of this paper is to reveal the effects when controlling humidity and airflow using the whole ceiling-type air conditioner compared to a commercialized concentrated exhaust air conditioner (normal-type air conditioner) under the same temperature. Salivary α-amylase activity (SAA) was used as an index of sympathetic nervous activity. An acute experiment for a 15 min period was conducted using 12 healthy young female adults. No significant differences in room and skin temperatures were observed between the whole ceiling-type air conditioner and the normal-type air conditioner. The whole ceiling-type air conditioner showed 11.1% lower humidity than the normal-type air conditioner. The whole ceiling-type air conditioner showed one-thirteenth the airflow of the normal-type air conditioner. As a result, the PMV of the whole ceiling-type air conditioner was more comfortable level than the normal one. Moreover, subjective evaluation questionnaire revealed a significant difference was observed in wind perception (windy). The SAA of subjects under the whole ceiling-type air conditioner showed significantly low values compared with the normal-type air conditioner. It was found that the subject's sympathetic nervous activity has been inactivated under the conditions of the whole ceiling-type air conditioner. Thus, it was revealed that the whole ceiling-type air conditioner provides a more comfortable air environment by reducing physical stimulations to humans.     

Simulation of a VAV air conditioning system in an existing building for the cooling mode

In this study, simulation of a variable air volume (VAV) air conditioning system in an existing office building is presented for the cooling mode. A building simulation package was used for the simulation [DOE, EnergyPlus Engineering Document, Version 1.3., U.S. Department of Energy, Washington, DC, 2005]. The design information of the existing office building, the actual number of the internal load sources such as occupants, lighting, office equipments and the manufacturer's data for the existing rooftop unit (RTU) and the VAV boxes were used in the building simulation package. The simulation results; RTU power consumption, indoor zone temperature and relative humidity, were validated with the data obtained from the on-site measurements performed in the existing office building under the same outdoor conditions. It was found that 71.1% of all simulated power consumption data falls within ±15% range from the experimental data. The reason for the existence of some data out of band is due to the possible errors associated with the difference in the solar data used for the location 40 km away from the experimental location. It was found that 90.6-94.7% of the indoor temperature experimental data fall within ±1.5 °C range from the simulated data, and 88.3-91.3% of the indoor relative humidity data fall within ±18% range from the simulated data.     

Experimental study on dehumidifier and regenerator of liquid desiccant cooling air conditioning system

A new type of air conditioning system, the liquid desiccant evaporation cooling air conditioning system (LDCS) is introduced in this paper. Desiccant evaporation cooling technology is environmental friendly and can be used to condition the indoor environment of buildings. Unlike conventional air conditioning systems, the system can be driven by low-grade heat sources such as solar energy and industrial waste heat with temperatures between 60 and 80 °C. In this paper, a LDCS, as well as a packed tower for the regenerator and dehumidifier is described. The effects of heating source temperature, air temperature and humidity, desiccant solution temperature and desiccant solution concentration on the rates of dehumidification and regeneration are discussed. Based on the experimental results, mass transfer coefficients of the regeneration process were experimentally obtained. The results showed that the mean mass transfer coefficient of the packing regenerator was 4 g/(m² s). In the experiments of dehumidification, it was found that there was maximal tower efficiency with the suitable inlet humidity of the indoor air. The effective curves of heating temperature on the outlet parameters of the regenerator were obtained. The relationships of regeneration mass transfer coefficient as a function of heating temperature and desiccant concentration are introduced.     

Modeling solar-driven ejector refrigeration system offering air conditioning for office buildings

A lumped method combined with dynamic model is proposed for use in investigating the performance and solar fraction of a solar-driven ejector refrigeration system (SERS) using R134a, for office air conditioning application for buildings in Shanghai, China. Classical hourly outdoor temperature and solar radiation model were used to provide basic data for accurate analysis of the system performance. Results indicate that during the office working-time, i.e., from 9:00 to 17:00, the average COP and the average solar fraction of the system were 0.48 and 0.82 respectively when the operating conditions were: generator temperature (85 °C), evaporator temperature (8 °C) and condenser temperature varying with ambient temperature. Compared with traditional compressor based air conditioner, the system can save upto 80% electric energy when providing the same cooling capacity for office buildings. Hence, the system offers a good energy conservation method for office buildings.     

Application of a closed-loop oscillating heat pipe with check valves (CLOHP/CV) on performance enhancement in air conditioning system

The objective of this paper was to study the application and working fluid type of a closed-loop oscillating heat pipe with check valves on energy consumption in split type air conditioning system. In the experiment, the CLOHP/CV was fabricated from the copper tube with the diameter of 2.03 mm. In the usual range of 20-27 °C indoor design temperature and 50% relative humidity. R134a, R22 and R502 refrigerant was used as working fluid in the CLOHP/CV set for this study. In comparison of the type with a conventional air conditioning system and that with the CLOHP/CV air conditioning system, the results have shown that; the new cooling load had increased 3.6%, the latter gave the highest value of 14.9%, 17.6% for COP and EER, respectively. The highest value of heat flux was 5.19 kW/m² with R134a was used as the working fluid, at overall operating temperature. The results of this study are expected to guideline as they improve the performance of the air conditioning system in buildings, which reduce its energy consumption.     

Development and testing of two-stage evaporative cooler

Evaporative cooling has been proved as an effective method of storage of fruits and vegetables of moderate respiration rates. Therefore, a modified evaporative cooler named two-stage evaporative cooler (TSEC) has been developed to improve the efficiency of evaporative cooling for high humidity and low temperature air conditioning. Two-stage evaporative cooler consists of the heat exchanger and two evaporative cooling chambers. The performance of cooler has been evaluated in terms of temperature drop, efficiency of the evaporative cooling and effectiveness of TSEC over single evaporation. The temperature drop through TSEC ranged from 8 to 16 °C. With the several observations for diurnal runs, it was observed that TSEC could drop the temperature up to wet bulb depression of ambient air and provided the 90% relative humidity. Efficiency of single evaporation was 85–90%. Effectiveness of the two-stage evaporative cooling was found to be 1.1–1.2 over single evaporation. The two-stage evaporative cooler provided the room conditions as 17–25 °C temperature and 50–75% relative humidity, which can enable to enhance the shelf-life of wide range of fruit and vegetables of moderate respiration rates.     

The study of energy-saving strategy for direct expansion air conditioning system

Most air conditioning, energy-saving research has focused on the chiller system, the most effective energy-saving procedure of its kind would be the use of forced downtime or load shedding control methods. However, the use of forced downtime control methods on direct expansion systems, while saving energy, would be at the expense of increasing room temperature, leading to the discomfort of the inhabitants. This research focused on the direct expansion system and used periodic downtime control methods to execute energy-saving procedures, thus providing reasonable temperature control and saving energy at the same time. According to the results, by reducing the periodic downtime, we can improve unstable temperature problems; i.e. operating for 15 min and downtime for 5 min, provided the optimal energy-saving efficiency, saving 21.66% of energy. However, the percentage of high room temperatures during this downtime period was 40.43%, this meant that if we wanted to save energy, we would have to sacrifice comfort; if we wanted more comfort, then we have to select an operating mode that was secondary to operating for 10 min and downtime for 5 min. We also discovered that if the air conditioner manufacturer modified the embedded program and adjusted the limit for upper temperatures of the settings upward by 1 °C, users would save 7.22% of energy; this was a procedure that was more direct and effective than any other energy-saving requisition.     

直接蒸发冷却空调机性能研究

分析了影响直接蒸发冷却空调机性能的因素,然后对天然植物纤维填料式直接蒸发冷却空调机性能进行了实验研究并获得了相关性能曲线。研究结果表明,直接蒸发冷却空调机在我国西北干旱和半干旱地区降温加湿效果很好,完全可以达到舒适性要求,是一种节能的绿色空调;天然植物纤维填料阻力较大,但降温加湿效果更好。     

Experimental study on a residential temperature-humidity separate control air-conditioner

According to the temperature and moisture characteristics and current problems experienced in the Yangtze River Area, a temperature-humidity separate control air conditioner was developed. This unit can remove indoor sensible heat and latent heat load separately, and adjust indoor temperature and humidity respectively, thus improve indoor comfort and reduce energy consumption. The air-conditioner consists of an air cooling evaporator and a water cooling evaporator. Orthogonal experiments were designed to study the influence of outdoor temperature, indoor temperature, indoor humidity, compressor frequency, and refrigerant distribution ratio in air cooling evaporator (RDRAE) on the unit performance. The results showed that the dehumidification capacity ranged from 0 to 4.02 kg/h; the EER ranged from 2.71 to 4.57; the cooling capacity ranged from 6822 to 13,080 W. The results can help to make the control logic of the unit, and be used as the basis of energy consumption calculation. Units with temperature and humidity separate control could save about 15.6% of the cooling energy consumption against traditional residential air-conditioner, and 47.8% against the traditional residential air-conditioner that could control both indoor temperature and humidity.     

Impact of individually controlled facially applied air movement on perceived air quality at high humidity

The effect of facially applied air movement on perceived air quality (PAQ) at high humidity was studied. Thirty subjects (21 males and 9 females) participated in three, 3-h experiments performed in a climate chamber. The experimental conditions covered three combinations of relative humidity and local air velocity under a constant air temperature of 26 °C, namely: 70% relative humidity without air movement, 30% relative humidity without air movement and 70% relative humidity with air movement under isothermal conditions. Personalized ventilation was used to supply room air from the front toward the upper part of the body (upper chest, head). The subjects could control the flow rate (velocity) of the supplied air in the vicinity of their bodies. The results indicate an airflow with elevated velocity applied to the face significantly improves the acceptability of the air quality at the room air temperature of 26 °C and relative humidity of 70%.     

Condenser heat recovery with a PV/T air heating collector to regenerate desiccant for reducing energy use of an air conditioning room

This paper presents an experimental test along with procedures to investigate the validity of a developed simulation model in predicting the dynamic performance of a condenser heat recovery with a photovoltaic/thermal (PV/T) air heating collector to regenerate desiccant for reducing energy use of an air conditioning room under the prevailing meteorological conditions in tropical climates. The system consists of five main parts; namely, living space, desiccant dehumidification and regeneration unit, air conditioning system, PV/T collector, and air mixing unit. The comparisons between the experimental results and the simulated results using the same meteorological data of the experiment show that the prediction results simulated by the model agree satisfactorily with those observed from the experiments. The thermal energy generated by the system can produce warm dry air as high as 53 °C and 23% relative humidity. Additionally, electricity of about 6% of the daily total solar radiation can be obtained from the PV/T collector in the system. Moreover, the use of a hybrid PV/T air heater, incorporated with the heat recovered from the condenser to regenerate the desiccant for dehumidification, can save the energy use of the air conditioning system by approximately 18%.     

公共建筑空调内部霉菌生长模拟研究分析

空调系统和人们的生活息息相关,如果空调内部有霉菌生长,霉菌的孢子会跟随气流进入人们生活的区域,可能引起人们的不舒适感,以及一些健康问题。为了验证空调系统内霉菌生长的程度,采用WUFI-Bio模拟空调内部霉菌的生长情况,判断霉菌生长的程度。结果显示,空调内部确实存在不同程度的发霉情况,空调内部的部件在清洁程度不同时、温湿度不同时,空调内部的发霉情况会有所不同。人们在使用空调时应注意防治霉菌生长,注意保持空调内部清洁,并保持其干燥性。     

Thermal sensation of Hong Kong people with increased air speed,temperature and humidity in air-conditioned environment

In the warm and humid climate zone, air-conditioning (AC) is usually provided at working places to enhance human thermal comfort and work productivity. From the building sustainability point of view, to achieve acceptable thermal sensation with the minimum use of energy can be desirable. A new AC design tactic is then to increase the air movement so that the summer temperature setting can be raised. A laboratory-based thermal comfort survey was conducted in Hong Kong with around 300 educated Chinese subjects. Their thermal sensation votes were gathered for a range of controlled thermal environment. The result analysis shows that, like in many other Asian cities, the thermal sensation of the Hong Kong people is sensitive to air temperature and speed, but not much to humidity. With bodily air speed at 0.1–0.2 m/s, clothing level 0.55 clo and metabolic rate 1 met, the neutral temperature was found around 25.4 °C for sedentary working environment. Then recommendations are given to the appropriate controlled AC environment in Hong Kong with higher airflow speeds.     

Research on seasonal indoor thermal environment and residents' control behavior of cooling and heating systems in Korea

Indoor thermal environments and residents' control behavior of cooling and heating systems were investigated in Seoul, Korea and compared with the results of previous studies. Twenty-four houses in summer, six houses in autumn and 36 houses in winter were used in this study. The measurement of temperature, humidity and air conditioner usage behavior was carried out. The clo-value, thermal comfort, sensation and basic data of the houses were also investigated. The indoor thermal environment in the summer had a high temperature and a high humidity ratio compare to standard comfort zone. Most of the indoor thermal environments at the time of starting the air conditioner in the summer were out of the comfort zone. Some of the data recorded while the air conditioner was stopped were in the comfort zone, but in many cases the temperature was relatively higher than comfort zone. Most indoor climate distributions in the winter were in the comfort zone and the indoor climate in autumn coincided well with the criteria of the comfort zone. Compared with results of previous studies in these 25 years, indoor ambient average temperature in winter has increased and the comfort temperature has increased in the heating period and decreased in the cooling period. This result indicates that the development of an HVAC system has created an expectation of comfort for residents and has shifted their thermal comfort zone warmer in winter and cooler in summer.     

Performance analysis of the building envelope: A case study of the Main Hall,Shinawatra University

The envelope of the Main Hall, Shinawatra University has been designed to provide protection from energy gain. According to initial estimates, the Main Hall could achieve an overall thermal transfer value (OTTV) of 10.16 W/m², which is four times lower than those recommended by the Thai national standard. This study aims to evaluate the actual energy performance of the Main Hall building envelope using field measurements and simulations. The air temperature, surface temperature, and relative humidity were measured at frequent intervals, both indoors and outdoors. Hourly average meteorological data for insolations were utilized in order to calculate the solar gain by light transmission. Based on the empirical data, the energy fluxes through the envelope on eight different orientations were simulated and the average value was found within 7% of the estimated OTTV. Using the same empirical data for the outdoor condition, simulations of other common types of building envelope in Thailand were carried out for comparison. The results of the analysis show that the Main Hall's lightweight and highly insulated building envelope outperforms other commonly used heavyweight envelopes in preventing building energy gain in the hot-humid climate of Thailand. Although the use of the lightweight and highly insulated envelope helps reduce the operating and investment costs of the air conditioning system as well as the cost of building structure, it also increases the investment cost of the envelope substantially. However, the life cycle cost analysis (LCCA) reveals that the life cycle cost (LCC) of the Main Hall envelope is the most economical, and the increased investment cost of the Main Hall envelope requires a discounted payback period of only 3–5 years, depending on the envelope types used in the comparison. Furthermore, it should be noted that greater savings and a more favorable pay back period could be obtained if this highly energy efficient envelope is applied to other typical buildings, especially high-rise structures in urban areas.     

某实验楼恒温恒湿空调改造工程设计、安装及调试

本文介绍了某实验楼恒温恒湿空调改造工程的设计、安装及调试。空调设备采用风冷恒温恒湿空调机组,共分8个独立的空调系统。本文总结了该工程从设计、安装到调试全过程的一些具体做法和体会。     

Thermal effect of temperature gradient in a field environment chamber served by displacement ventilation system in the tropics

The effect of vertical air temperature gradient on overall and local thermal comfort at different overall thermal sensations and room air temperatures (at 0.6 m height) was investigated in a room served by displacement ventilation system. Sixty tropically acclimatized subjects performed sedentary office work for a period of 3 h during each session of the experiment. Nominal vertical air temperature gradients between 0.1 and 1.1 m heights were 1, 3 and 5 K/m while nominal room air temperatures at 0.6 m height were 20, 23 and 26 °C. Air velocity in the space near the subjects was kept at below 0.2 m/s. Relative humidity at 0.6 m height was maintained at 50%. It was found that temperature gradient had different influences on thermal comfort at different overall thermal sensations. At overall thermal sensation close to neutral, only when room air temperature was substantially low, such as 20 °C, percentage dissatisfied of overall body increased with the increase of temperature gradient. At overall cold and slightly warm sensations, percentage dissatisfied of overall body was non-significantly affected by temperature gradient. Overall thermal sensation had significant impact on overall thermal comfort. Local thermal comfort of body segment was affected by both overall and local thermal sensations.     

高精度空气接收混合箱的仿真设计

根据空调器测试标准对温湿度取样装置的要求,比较了空气焓差法测试系统中空气接收混合箱的几种结构,并通过CFD模拟进行了优化设计。仿真结果表明,在接收箱内加装带有挡流板和导风格栅的混合器,对气流的均匀扩散、测量精度的提高有明显效果。     

Estimating the effects of ambient conditions on the performance of UVGI air cleaners

Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure mercury vapor lamps to control biological air contaminants. Ambient air velocity and temperature have a strong effect on lamp output by influencing the lamp surface cold spot temperature. In-duct UVGI systems are particularly susceptible to ambient effects due to the range of velocity and temperature conditions they may experience. An analytical model of the effect of ambient conditions on lamp surface temperature was developed for three common lamp types in cross flow from a convective–radiative energy balance assuming constant surface temperature. For one lamp type, a single tube standard output lamp, UVC output and cold spot temperature data were obtained under typical in-duct operating conditions. Over an ambient temperature range of 10–32.2 °C and an air velocity range of 0–3.25 m/s, measured cold spot temperature varied from 12.7 to 41.9 °C and measured lamp output varied by 68% of maximum. Surface temperatures predicted by the heat transfer model were 6–17 °C higher than corresponding measured cold spot temperatures, but were found to correlate well with cold spot temperature via a two-variable linear regression. When corrected using this relationship, the simple model predicted the cold spot temperature within 1 °C and lamp UVC output within ±5%. To illustrate its practical use, the calibrated lamp model was employed in a simulation of the control of a contaminant in a single-zone ventilation system by an in-duct UVGI device. In this example, failure to account for the impact of ambient condition effects resulted in under-prediction of average space concentration by approximately 20% relative to a constant output system operating at maximum UVC output.     

金属填料直接蒸发式空调机性能研究

对铝箔金属填料直接蒸发冷却空调机进行了实验研究。分析了进口空气干球温度、相对湿度对空调机降温及冷却效率的影响,为直接蒸发冷却式空调机性能的提高具有一定的参考意义。