共查询到19条相似文献,搜索用时 171 毫秒
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电加热相变储能式地板采暖系统试验研究 总被引:1,自引:0,他引:1
建立了一种新型电加热相变储能式地板采暖系统(相变系统),分析了其稳定性、舒适性和经济性。通过用DSC法选取相变材料,其熔点和潜热分别为44.24℃和128.52kJ/kg,应用此相变材料于电加热地板采暖系统,并与普通电加热地板采暖系统(普通系统)进行了两个供暖季节的对比实验研究,分析相变材料的稳定性,测量系统和室内外空气的温度变化以及不同系统的耗电量。表明了相变系统蓄换热性能好,白天的电热负荷基本转移到夜间低谷电价时段。相比普通系统,其运行费用低.3.2a可收回投资。新型的相变系统充分利用了相变材料可储存廉价低谷电热能,在峰平时段释放的特点,有效实现了移峰填谷,具有很好的应用前景。 相似文献
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工业余热浪费严重、利用率较低且实际应用过程中受到时间和空间的限制,需要高效蓄热技术和装置来解决此类问题。提出一种将多通道平行流扁管与紧凑式翅片相结合的新型相变蓄热器,以水为载热流体,月桂酸为相变材料。实验研究了载热流体注入方式、流量、入口温度对蓄热器蓄/放热性能的影响,并分析小温差下蓄热器的传热特性。结果显示,该蓄热器相变材料填充率为82.5%,紧凑式翅片的采用极大强化了相变材料侧换热过程,蓄/放热性能优良。当载热流体入口温度分别为45℃和41℃时,相变材料约在270 min和75 min完成相变,最小蓄/放热温差可达2℃,最小温差时的平均蓄热比功率为25.18 W/kg,平均取热比功率为20.23 W/kg。 相似文献
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提出一种基于太阳能热风供暖系统的多级相变通风吊顶新型供暖末端。建立多级相变太阳能通风吊顶传热数值模型,对比研究了单级、两级和三级相变太阳能通风吊顶的蓄放热特性,分析相变材料的长度配比、空气流速对供暖末端蓄放热性能的影响规律。研究结果表明,与采用单一相变材料的通风吊顶相比,多级相变太阳能通风吊顶在蓄放热过程中出口平均温度差异更小。相变蓄热级数为3时,通风吊顶的蓄、放热效率及相变材料利用率改善最大,分别为6.5%、7.9%和25.1%,各级相变材料长度的配比为1∶1∶1时,蓄、放热效率及相变材料利用率最佳,分别为51.0%、88.7%和93.9%。空气流速不宜大于1.6 m/s,在保证供暖效果的前提下可适当减小空气流速。 相似文献
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This study presents a model-based control strategy for a novel dedicated outdoor air-chilled ceiling (DOAS-CC) system with the aim of optimizing the overall system performance. The DOAS-CC system incorporates liquid desiccant dehumidification and membrane-based total heat recovery technologies. Simplified but reliable models of major components in the DOAS-CC system are firstly developed to predict the system performance. A cost function is then constructed to minimize total energy consumption while properly maintaining thermal comfort reflected by indoor air temperature and relative humidity. Genetic algorithm is used to search for optimal set-points of the supply air temperature and humidity ratio of the dedicated outdoor air subsystem as well as the supply water temperature. The performance of this strategy is tested and evaluated with different control settings in a simulated multi-zone space served by the DOAS-CC system under various weather conditions. The results show that optimized control variables produced by the optimal strategy can improve the system energy performance and maintain indoor thermal comfort. 相似文献
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Indoor thermal environment is important as it affects the health and productivity of building occupants. Direct expansion (DX) air conditioning (A/C) units are commonly used for environmental control in small- to medium-scaled buildings. This paper reports on an experimental study to investigate the indoor thermal comfort characteristics under the control of a DX A/C unit having variable-speed compressor and supply fan at a fixed space cooling load but having three different ratios between its sensible part and latent part. The experimental results suggested that under a fixed indoor total cooling load with three different space sensible heat ratios (SHRs) of 0.92, 0.72 and 0.62, varying both speeds of compressor and supply fan in the DX A/C unit would influence indoor thermal comfort. Furthermore, when a DX A/C unit having variable-speed compressor and supply fan is used for indoor thermal comfort control under abnormal indoor load conditions, its ability of indoor thermal comfort control through varying compressor speed and supply fan speed may be duly restricted. 相似文献
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测量地板辐射与下送风复合式供冷系统运行过程中的室内空气温湿度、围护结构表面温度等室内环境参数,分析室内温湿度、热舒适性、系统换热量的变化规律,并对室内空气环境进行影响因素分析。实验结果表明:室内空气绝对湿度较室内空气温度达到稳定需要的时间更短;MRT(mean radian temperature)、OT(operation temperature)和PMV-PPD值在系统开启后第1.0 h减小速率最大,1.5 h后逐渐趋于稳定,此时,PMV约为0.49,PPD约为10%,在热舒适范围内;地板净辐射换热量、对流换热量和总换热量在系统开启后的1.5 h内递增,然后趋于稳定,此时,地板辐射换热量约为37 W/m~2,占总换热量的47%;室内空气温度和作用温度均随室外综合温度、室内发热量、供回水平均温度和送风温度的增加而增加,当室外综合温度较低或较高,或室内发热量较低,或供回水平均温度较低时,室内空气温度和作用温度变化梯度较小,室内空气温度和作用温度随送风温度增加而增加的速率近似呈线性。 相似文献
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Integrated control by controlling both natural ventilation and HVAC systems based on human thermal comfort requirement can result in significant energy savings. The concept of this paper differs from conventional methods of energy saving in HVAC systems by integrating the control of both these HVAC systems and the available natural ventilation that is based on the temperature difference between the indoor and the outdoor air. This difference affects the rate of change of indoor air enthalpy or indoor air potential energy storage. However, this is not efficient enough as there are other factors affecting the rate of change of indoor air enthalpy that should be considered to achieve maximum energy saving. One way of improvement can be through the use of model guide for comparison (MGFC) that uses physical-empirical hybrid modelling to predict the rate of change of indoor air potential energy storage considering building fabric and its fixture. Three methods (normal, conventional and proposed) are tested on an identical residential building model using predicted mean vote (PMV) sensor as a criterion test for thermal comfort standard. The results indicate that the proposed method achieved significant energy savings compared with the other methods while still achieving thermal comfort. 相似文献
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This paper examines optimal control strategies of variable air volume air conditioning system. The control strategies included a base control strategy of fixed temperature set point and two advanced strategies for insuring comfort and indoor air quality (IAQ). The first advanced control adjusts the fresh air supply rate and the supply air temperature to maintain the temperature set point in each zone while assuring indoor air quality. The second strategy controls the fresh air rate and the supply air temperature to maintain an acceptable thermal comfort and IAQ in each zone. The optimization problem for each control strategy is formulated based on the cost of energy consumption and constrained by system and thermal space transient models. The optimization problem is solved using genetic algorithm. The optimization scheme/model is applied to a case study for a building floor in Beirut weather. The thermal space and system component models were validated for the base strategy using Visual DOE 4.0 software [Architectural Energy Cooperation, San Francisco, USA; 2005 〈www.archenergy.com〉]. Energy savings up to 30.4% were achieved during the summer season of four months with the optimized advanced strategies when compared with the conventional base strategy while comfort and IAQ were satisfied. 相似文献
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变风量空调系统中的实时优化节能控制 总被引:8,自引:1,他引:7
在对变风量空调系统局部控制的分析基础上,利用其变风量末端风门的开度作为各区域相对负荷的指示信号,提出送风静压的实时优化控制方案;同时,针对新的ASHRAE通风标准,还提出了基于室内人数检测和焓控制的新风实时优化控制方案。试验结果证明,同常规的控制方案相比,在保证室内热舒适性和空气质量的前提下,这两个方案分别有较好的节能作用。综合采用两种优化方案,系统不仅能够达到节能的目的,而且在较小负荷情况下能够提高室内空气的品质。 相似文献
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In this study a low-energy-consumption technique to enhance passive cooling and natural ventilation in a solar house, using a system consisting of a Solar Chimney (SC) and an Evaporative Cooling Cavity (ECC) has been proposed. The capability of the system to meet the required thermal needs of individuals and the effects of main geometric parameters on the system performance has been studied. The dependence of the system performance on outdoor air temperature has been studied to determine the operative conditions for appropriate effectiveness, regarding thermal comfort criteria. To determine the heat and mass transfer characteristics of the system, a mathematical model based on conservation equations of mass and energy has been developed and solved by an iterative method. The findings show that the system is capable of providing good indoor air condition at daytime in a living room, even with poor solar intensity of 200 W/m2. The results show that when the relative humidity is lower than 50%, the system can make good indoor air condition even at 40 °C, and a higher performance is achieved using ECC with cocurrent configuration. It is found that the proposed system may be applied successfully in hot arid climates to fulfill the indoor thermal comfort expectations. 相似文献
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An experimental investigation of dehumidifying and reheating performances of a dual‐evaporator heat pump system in electrified vehicles 下载免费PDF全文
Climate control system in electrified vehicle is quite different from traditional internal combustion engine vehicle, as it cannot use the wasted coolant heat from engine to keep warm of the cabin. For the dehumidifying and reheating air in the electrified vehicle cabin, the use of a dual‐evaporator heat pump system could improve the total energy utilization efficiency of the climate control system. In this study, an experimental dual‐evaporator heat pump system was set up to investigate dehumidifying and reheating efficiency of a cabin in electrified vehicle. Two dehumidifying modes were chosen in this experiment. One was single‐evaporator mode with indoor evaporator only, and the other was dual‐evaporator mode with both indoor and outdoor evaporators. The dual‐evaporator dehumidifying mode shows higher heat capacity, coefficient of performance, and outlet air temperature, while it has quite lower moisture extraction rate and specific moisture extraction rate compared to the single‐evaporator dehumidifying mode. Therefore, a hybrid dehumidifying and reheating method was suggested as a possible option for realization of energy conservation without sacrifice of thermal comfort for passengers. 相似文献