Search

It is noticed that the building envelope thermal load affects the indoor thermal environment and operation of the air conditioning system due to the heat transfer through the envelope. The variation of indoor thermal environment will directly affect the performance of the air conditioning system. To weaken even eliminate the effects of envelope thermal load, PCM was integrated in the building envelope. The effects of PCM on variation of return air temperature in a bedroom in a coastal city was studied and compared with the traditional building envelope. The characteristics of PCM, like the melting temperature and amount of PCM were also investigated. [ABSTRACT FROM AUTHOR]

Task/ambient air conditioning (TAC) system is reported to be an energy efficient technology with available methods to control thermal comfortable level for sleeping environments. However, for real application the varied envelope thermal load should be considered. To determine the optimum operation under different envelope thermal load, an optimization of the TAC system operation was carried out in this study. A multi-objective optimization approach named TOPSIS method was used to evaluate the integrated performance of the TAC system. Finally, the ranking of the selected study cases was obtained and the optimum operation was achieved. [ABSTRACT FROM AUTHOR]

Short-term forecasting of air-conditioning cooling load of shopping mall is hard with much accuracy due to its chaotic and non-linear characteristic. Four forecasting algorithms based on machine learning are illustrated in this paper including Chaos-SVR, WD-SVR, SVR and BP, whose predicting performances are compared. For Chaos-SVR, the selection of lag time and embedding dimension during phase space reconstruction are described, while for WD-SVR, the modeling process of DB2 is proposed. Furthermore, the optimization of the hyper-parameters for SVR model is also presented. It’s shown that these four approaches have different characteristics which are suitable for different types of cooling load time series. [ABSTRACT FROM AUTHOR]

The large chilled water plants with multiple chillers were widely used at large-scale public since a reduced starting in-rush current and a reduced power cost under part load conditions. It is important that the cooling load should be allocated to individual chillers operating in order to optimize their aggregate COP of the multi-chiller system. In this paper, an optimization method was developed to optimize the load sharing strategies for a multiple-chiller system, based on the operational data of a multi-chiller system in a shopping mall. The first step was that using the Least Squares Method (LMS), the parameters of efficiency performance models of each chiller were identified based on the operational data of a multi-chiller system in a shopping mall. The second step is that a genetic algorithm (GA) was used to optimize the load sharing strategy for the multiple-chiller system, resulting in optimizing their aggregate COP of the multi-chiller system. Lastly, this optimization method developed was applied to control the multi-chiller system in the shopping mall under a typical summer day. The results that compared with the conventional control method, the optimization control method can reduce the energy consumption by 3511.26 kW*h in the summer typical day. It can seen that the optimization method developed in this paper can help reduce the energy consumptions of the multi-chiller system in the shopping mall. Moreover, there was a larger energy saving potential in summer. [ABSTRACT FROM AUTHOR]

Phase change materials have found wide applications in recent decades in different fields due to their good thermal performance in energy systems. These fields include green building envelope, industry thermal energy storage, battery thermal management, power peak regulation, smart thermal fibers, and bio-medical, etc. These applications are mainly limited by their phase change temperatures and latent heat values, which makes topics around characteristic improvement for binary organic phase change materials very hot. Thus, the thermal stability study on organic binary phase change materials used in thermal energy storage applications is fundamental and meaningful. In this study, an experimental investigation on thermal stability of three types of organic binary PCMs was conducted, which are very frequently-used in building services and industry waste energy recovery. As concluded, in view of phase change temperature and heat of fusion, Capric acid & Myristic acid has the best thermal stability and reliability performance among the mentioned three composite materials. This study makes contributions to phase change materials choosing and system life-span design optimization. [ABSTRACT FROM AUTHOR]

Sleep can help people overcome physical and psychological fatigue, and sleep is very important to one’s memory. The total insulation value of a bedding system is a significant factor, which affects remarkably the thermal comfort for sleeping environments. This paper reports a study on the effects of different bedding systems on thermal comfort to quantify the sensitivity coefficient used for calculating PMV in sleeping environments. Firstly, the experimental materials and methods were described in detail. Then, the experimental results and their analysis of the effects of different bedding systems on thermal comfort, in terms of skin temperatures and thermal sensations, are reported. Finally, the sensitivity coefficient used for calculating PMV in sleeping environments is regressed and further discussions are presented. The experimental results showed that the bedding systems affected remarkably mean skin temperatures, and especially the local skin temperature at forearm posterior. The relationship between the local skin temperature at forearm posterior and thermal sensation of subjects was established, suggesting that the skin temperatures was an important factor that influences the human’s sensation during sleep. A sensitivity coefficient with a higher value of 0.1733 was regressed by the experimental results, and can be used for calculating PMV in sleeping environment. [ABSTRACT FROM AUTHOR]

There has been an increasing concern on thermal comfort in sleeping environments and its associated energy use in the past few years. To improve the thermal environment and reduce energy use of air conditioning in bedrooms, task/ambient air conditioning (TAC) can be applied and was studied previously. Due to the variation of the envelope thermal loads in a bedroom during night, it is necessary to study the thermal environment inside the bedroom and the energy use of a TAC system for the bedroom at varying envelope thermal loads. Therefore, this paper reports on a numerical study on a TAC system applied to a bedroom with different envelope heat gains. PMV and EUC (energy utilization coefficient) values were evaluated, respectively. The study results indicated that when envelope thermal loads was higher, the advantage of the TAC system in energy saving was greater for the same thermal comfort level. However, it should be noted that a higher envelope thermal load could also resulted in the non-uniformity in air flow and air temperature distributions, leading to a possible uncomfortable micro environment. [ABSTRACT FROM AUTHOR]

A bed-based TAC system applied to sleeping environments has been developed and its performances experimentally and numerically studied, and the study results are reported in this paper. Firstly, a detailed description of an experimental rig for the bed-based TAC system at two settings is presented with a return air inlet on the wall (Setting 1) and with a return air plenum and inlet placed under the bed (Setting 2). Secondly, the experimental results on the operating performances of the bed-based TAC system at the two settings in terms of thermal environmental control and energy saving are analyzed and reported. Thirdly, to supplement the experimental study for a more detailed analysis on air temperature and flow fields, a follow-up numerical study was carried out and is reported. Both the experimental and numerical study results suggested that the bed-based TAC system at Setting 2 performed better in controlling thermal environment in an occupied zone but with a relatively poorer energy saving performance, as compared to that at Setting 1. [ABSTRACT FROM AUTHOR]

Abstract: A human being spends approximately one-third of his/her life in sleep. Sleep can help people overcome tiredness, and is very important to one''s memory. With the gradual understanding of the influence of thermal parameters in a sleeping environment on the quality of sleep, different thermal environmental control approaches, such as electric blankets, space heating for cold sleep environments and circulation fans and air-conditioning for hot sleep environments, have been used to maintain a suitable thermal environment for sleep, so that sleep quality could not be adversely affected. In this review paper, firstly, the concept of thermal comfort applicable to sleeping environments is introduced and the relevant studies reviewed. Secondly, the review of the two important issues related to air-conditioning for sleeping environments in tropics and sub-tropics, i.e., night-time space cooling load characteristics, and ventilation requirement for a sleeping person, is presented. Thirdly, different air-conditioning systems used in sleeping environments and these related energy consumptions are reviewed, with an emphasis on bed-based (task/ambient conditioning) TAC applicable to a sleeping environment, which could help save more energy without scarifying the thermal comfort of a sleeper and indoor air quality. Finally, a number of research areas where future studies are needed are reported, including developing optimized control strategies for air-conditioning systems for sleeping environments according to night-time space cooling load characteristics, and new TAC systems applicable to a sleeping environment for greater energy saving. [Copyright &y& Elsevier]

Abstract: Thermoregulation and sleep interacted each other and thermoregulatory responses were present during sleep to maintain small oscillations of core temperature of a sleeping person. In order to improve sleep quality, it was necessary to investigate the thermoregulatory responses of a sleeping person. This paper reports on a study of developing a four-node thermoregulation model for predicting thermal physiological responses of a sleeping person, based on the existing Gagge’s two-node model. Firstly, the Gagge’s two-node model is introduced in detail. This is followed by reporting the necessary modifications to Gagge’s two-node model for developing the four-node thermoregulation model for a sleeping person. Thirdly, the four-node thermoregulation model is presented in detail. Lastly, the validation of the four-node thermoregulation model by comparing the predicted thermal physiological responses, including skin and core temperatures, using the model developed with the experimental data previously obtained by others is presented. The comparison results showed that the four-node thermoregulation model developed could be used to predict the thermal physiological responses of a sleeping person, with an acceptable accuracy. [Copyright &y& Elsevier]

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]