New type of fresh air processor with liquid desiccant total heat recovery

A liquid desiccant total heat exchanger and small capacity refrigeration cycle combined fresh air processor is proposed here in this paper, in order to improve indoor air quality and decrease the energy consumption of the air-conditioning system. Operating principles of both the total heat recovery device and fresh air processor using liquid desiccant are presented in details. Experimental tests of the fresh air processor installed in a hospital show that energy efficiency ratio (EER) is around 6.3–7.3 in the summer experimental conditions and 4.7–5.0 in the winter experimental conditions. Hour-by-hour simulation, which is based on the climate data in Beijing, shows that the average EER is 5.3 and 4.3 in summer and winter period, respectively. Liquid desiccant has the potential to remove a number of pollutants, avoiding cross contamination. Furthermore, in summer fresh air is dehumidified by contacting liquid desiccant instead of 7 °C chilled water, which avoids wet surfaces in the air-conditioning system and much higher indoor air quality can be achieved.     

溶液除湿空调在高温高湿地区的应用研究

设计了一种新型的溶液除湿装置。综合利用太阳能、天然水源、热回收和溶液除湿技术,对新风进行分阶段除湿,同时,利用太阳能和室内排风对溶液进行再生,克服了传统溶液除湿空调技术在高温高湿地区应用过程中的局限性。结果表明,与传统溶液除湿方案相比,该系统的溶液循环量减小,运行能耗降低,对太阳能的依赖程度降低,溶液的吸湿效率和再生效率提高。     

Application of desiccant systems for improving the performance of an evaporative cooling-assisted 100% outdoor air system in hot and humid climates

The purpose of this study was to enhance the energy-saving potential of an indirect and direct evaporative cooling-assisted 100% outdoor air system (IDECOAS) by integrating it with either a solid or liquid desiccant system. The desiccant system can be installed either at the scavenger air side of the indirect evaporative cooler (IEC) to enhance its effectiveness or at the primary air side of the IEC to reduce the latent load of outdoor air. The operating energy consumption affected by the location and type of the desiccant unit integrated with IDECOAS was simulated under three different hot and humid climates using TRNSYS 17 integrated with commercial equation solver programme. And then, the most energy-conservative configuration was selected for each climate zone as the proposed system. The simulation results showed that configurations with the desiccant dehumidification unit located upstream of the IDECOAS consume 76–85% less cooling coil energy than those with the desiccant unit located downstream of the IDECOAS. It was also found that the liquid desiccant system saves 21–50% more primary energy than the solid one, when it is integrated with IDECOAS.     

In situ performance of independent humidity control air-conditioning system driven by heat pumps

A liquid desiccant based independent humidity control (IHC) air-conditioning system driven by heat pumps is presented in this paper. The system consists of a liquid desiccant fresh air processor and a high-temperature chilled water system. The operating principles of the fresh air processor and the whole system are presented in detail. Based on the in situ system installed in an ecological building of Shanghai Research Institute of Building Sciences (SRIBS), a performance investigation was performed in summer, 2007. The measurement results show that (1) the indoor temperature and humidity both are in the specified range; (2) the supply water temperature of the high-temperature refrigerator is higher than the corresponding indoor air dew point temperature, so no condensed water would be formed on the fan-coil unit (FCU) surface; and (3) the average coefficients of performances (COPs) of the fresh air processor and the high-temperature refrigerator are 6.24 and 4.38, respectively, and the average COP of the whole IHC system is 5.28.     

利用冷凝热再生的复合除湿空调除湿潜力分析

简要描述了利用冷凝热再生的复合除湿空调系统形式及其节能性特点;在热力学第一定律和热力学第二定律的基础上,分别以冷凝器和除湿转轮为控制体,建立了复合除湿空调的系统热力学模型,并给出模型求解框图,从而可以求得复合除湿空调系统的除湿量;最后,计算了在不同转轮效率和室内单位面积显热负荷下的系统单位面积除湿量,并讨论了新风量大小对结果的影响;结果表明,在现有转轮效率和常见单位面积负荷指标下,转轮的除湿量小于新风湿负荷（1次/h）,而降低新风量后（0.5次/h）,当转轮效率较高和室内显热负荷较大时,转轮能够承担新风湿负荷。     

溶液全热回收装置与热泵系统结合的新风机组

提出了一种以溶液为媒介的全热回收装置和热泵系统相结合的新风处理机。安装于某医院的新风机性能测试结果表明：测试条件下，新风机夏季性能系数为6．3～7．3，冬季性能系数为4．7～5．0。新风机中吸湿溶液能去除空气中多种污染物，可避免新风和室内排风之间的交叉污染。     

利用蒸发式冷凝器再生除湿溶液时传质系数的实验研究

建立了溶液再生式蒸发冷凝器实验台,利用冷凝热再生氯化锂除湿溶液,对影响空气与除湿溶液之间传质系数的主要因素进行了实验测试.在大量实验数据基础上,分析了除湿溶液质量流速及空气迎面风速对空气与液膜之间传质系数的影响,并回归得到了传质系数的经验公式,为利用低品位热源再生除湿溶液提供理论依据.     

Proposal for a new hybrid control strategy of a solar desiccant evaporative cooling air handling unit

Correctly controlled solar desiccant evaporative cooling is an interesting option for achieving savings in building air-conditioning consumption. The operation of this system (open loop cooling cycle) is strongly influenced by indoor and outdoor air conditions. This influence is characterized using numerical simulations. First the air conditioned room and the cooling system are simulated using a validated model of the desiccant wheel. Then the influence of each parameter of the desiccant air handling unit is evaluated. The third step is to assess the system cooling power for each operating mode with fluctuating outdoor and indoor air conditions. This allows for making relevant choices for a new control strategy taking into account both indoor and outdoor air conditions. This control strategy is tested for a whole cooling season and compared to a reference compression system with promising results, allowing for energy savings of about 40% for French climate.     

Theoretical simulation and experimental research on the system of air source energy independence driven by internal-combustion engine

Presents a new system of air source energy independence driven by internal-combustion engine (EIICE), which used natural gas or other fuels as an independent input energy, and could provide the heating, cooling and hot water for the buildings efficiently. It also could provide electricity for electric equipments of the system. The performance of air source EIICE system was investigated theoretically and experimentally. The experimental and simulation results indicated that the heat capacity of plate heat exchanger (P-HE), heat recovered from exhaust gas heat exchanger (EG-HE), input power of compressor, output power of engine and fuel consumption increased with the increase of the rotary speed, water flow rate of the P-HE and evaporation temperature. Heat recovered from the cylinder jacket heat exchanger (CJ-HE) increased with the increase of the rotary speed and evaporation temperature, but decreased with the increase of the water flow rate of P-HE. The coefficient of performance (COP_t) and primary energy ratio (PER_t) of air source EIICE system also increased with the increase of the water flow rate of P-HE and evaporation temperature, but decreased with the increase of the rotary speed.     

Energy-saving judgment of electric-driven seawater source heat pump district heating system over boiler house district heating system

As a renewable energy utilization system, the electric-driven seawater source heat pump district heating system is gaining popularity in some coastal areas. However, under what conditions can the system achieve its energy-saving effect and how to evaluate its energy-saving potential are not clear in practice. In this paper, an expression of the critical COP value of the heat pump unit for energy-saving (COP_h,c) is derived through the comparison of the system and the conventional boiler house district heating system in the energy consumption respect. On the other hand, the actual COP values of the heat pump unit (COP_h,a) are calculated by an experimental data regression model on the basis of the manufacturer's dataset. The comparison of the values of COP_h,c and COP_h,a makes the energy-saving judgment of an electric-driven seawater source heat pump district heating system and its energy-saving potential, if it has, readily available. It was found that both the heating district radius and the natural conditions of the seawater are the most important factors that determine the energy efficiency of the system. And through comparison, it was also found that the type of the fuel of the boiler has significant impact on the crucial index value of COP_h,c.     

燃气驱动的三级液体除湿空调系统及其特点分析

介绍了液体除湿空调系统的原理及其特点。基于分级除湿思想和能量梯级利用原则，提出了一种燃气驱动的三级液体除湿空调系统，系统由风机、除湿器、蒸发冷却器和再生器组成。除湿器采用三级液体除湿，通过对室内回风直接蒸发冷却进行全热回收，用回收的冷量冷却除湿过程，移去处理空气的潜热；蒸发冷却器由间接蒸发冷却器和直接蒸发冷却器两部分组成，前者间接冷却除湿后的空气，移去空气的显热，后者调节空气的温湿度；再牛器采用燃气驱动，实现沸腾蒸发和非沸腾蒸发结合的两效再生。该系统是一种节能环保的新型空凋系统，具有优化城市能源结构的功能。     

Efficiency of energy recovery ventilator with various weathers and its energy saving performance in a residential apartment

The energy recovery ventilator (ERV) is an effective method, which can transfer heat and moisture from the exhaust air into the outdoor fresh air to save energy in buildings. Nowadays, ERV has been widely used in the commercial, industrial and residential buildings in China. Its energy saving performance depends on a lot of factors, such as the outdoor environmental conditions, the enthalpy efficiency of the exchanger, and so on. Based on the relationship among sensible heat, latent heat and enthalpy efficiency, we analyzed the weighted coefficient equations for describing the performance of ERV in different climatic zones in China. According to China weather data, enthalpy efficiency of the exchanger mainly depends on sensible heat efficiency in winter and latent heat efficiency in summer. The energy simulations of a sample apartment in a residential building were made under different operation conditions to study the performance of ERV. The energy saving performances of the ERV were studied with five different outdoor climatic conditions, the enthalpy efficiency, fan power consumption of ERV and fresh air change rate. To improve energy saving performance, better efficient enthalpy exchange material and higher effiencient fans must be explored, while reasonable fresh air change rate as well as proper operation period according to local climate should also be carefully considered.     

溶液-湿空气热质交换过程的匹配研究

吸湿性溶液与空气的热质交换过程既有热量的交换又有质量的交换,提高该过程的可逆程度是提高溶液除湿空调系统性能的重要手段。在对溶液的性质进行合理简化的基础上,分析了溶液与空气的热质交换过程的流量比和过程需要吸收或释放的热量,得到在不同工况下,可逆过程所要求的流量比和应该补充或带走的热量。认为这一结论有助于溶液除湿空调流程的设计和相关参数的选取。     

新风和回风对液体除湿空调系统的影响

采用十字正交实验法对液体除湿新风处理机组在高温高湿工况下的除湿量进行了测定分析,结果表明：除湿量受新风含湿量、风量影响较大,受新风温度和回风温度、风量影响较小;并随着进口空气流量、含湿量、温度和回风量的增加而增大,随回风温度的升高而降低。     

Quasi-dynamic energy-saving judgment of electric-driven seawater source heat pump district heating system over boiler house district heating system

The electric-driven seawater source heat pump district heating system is a renewable energy utilization system, but this cannot guarantee the energy-saving effect of the system. The static energy-saving judgment between this system and the conventional boiler house district heating system was provided in a former research paper. However the static method has proved to be a very rough evaluation method and may lead to misjudgment as well. So a quasi-dynamic method, taking the total energy consumption during a whole heating season into consideration, is established in this paper. The energy-saving index turns out to be the expression of the lower limit of the average COP of the seawater source heat pump unit throughout the heating season (COP_h,mc). Then a case study is presented to show how the index of COP_h,mc and the actual average COP of the heat pump unit throughout the heating season (COP_h,ma) are calculated. The calculation results show that the quasi-dynamic method improves the calculation accuracy dramatically, and thus provides a better solution to the quantitative energy-saving evaluation of the electric-driven seawater source heat pump district heating system.     

香港地区溶液除湿与蒸发冷却复合系统的节能分析

本文提出了溶液除湿与蒸发冷却相结合的复合系统,并根据香港地区的气候条件和相关的空调设计参数,将该复合系统的能耗与一次回风空调系统的能耗进行对比.计算结果表明,在设计工况下复合系统的节能率为21.3%.当采用太阳能、地热等可再生能源或其它废热时,系统的节能率更大.结果表明该复合系统在香港具有较好的运用前景.     

Build-up and performance test of a novel solar thermal roof for heat pump operation

Global increase in energy demand and fossil fuel prices loaded ever-increasing pressure on identifying and implementing new means to utilise clean and efficient energy resources. Due to the environmental benefits, technical and economic possibilities of Solar-Assisted Heat Pump Systems, there has been a growing interest for such hybrid systems with a variety of system configurations for various climates. International Energy Agency Task 44 of the Solar Heating and Cooling Programme has recently started working on finding methods to most effectively use solar heat pump systems for residential use. In the present study, a novel solar thermal roof collector was developed by primarily exploiting components and techniques widely available on the market and coupled with a commercial heat pump unit. The proposed indirect series Solar-assisted Heat Pump system was experimentally tested and system performance was investigated. Yet, the analysis based on indoor and outdoor testing predominantly focuses on the solar thermal roof collector. A detailed thermal model was developed to describe the system operation. Also, a computer model was set up by using Engineering Equation Solver to carry out the numerical computations of the governing equations. Analyses show that the difference in water temperature could reach up to 18°C while maximum thermal efficiency found to be 26%. Data processing of the series covering the test period represents that Coefficient Performance of the heat pump (COP_HP) and overall system (COP_SYS) averages were attained as COP_HP?=?3.01 and COP_SYS?=?2.29, respectively. An economic analysis points a minimum payback period of about three years for the system.     

Performance of temperature and humidity independent control air-conditioning system in an office building

The temperature and humidity independent control (THIC) system, which controls indoor temperature and moisture separately, may be an attractive alternative to existing conventional HVAC systems for its prominent improvement on the overall system performance and utilization of low grade energy resources. In order to verify the effectiveness of THIC system, a pilot project has been implemented in an office building in Shenzhen, China. In the system, liquid desiccant fresh air handling units driven by heat pumps are utilized to remove the entire latent load of outdoor air supplied for the whole building, and chilled water at the temperature of 17.5 °C from chiller is pumped and distributed into dry fan coil units and radiant panels to control indoor temperature. This paper presents the results of field test of the system, which shows that the system can provide a comfortable indoor environment even in very hot and humid weather. The COP of the entire THIC system can reach 4.0. According to the energy usage data recorded from the year 2009, the energy consumption of the THIC system in the tested office building was 32.2 kWh/(m² yr), which demonstrates magnificent energy-saving potential compared with the conventional air-conditioning system (around 49 kWh/(m² yr)).     

溶液除湿空调新风机组冬季工况性能研究

提出了一种由溶液除湿新风机组和空气源热泵装置组合的新系统,利用MATLAB语言对该系统进行数值模拟计算和分析,结果表明:在西安地区冬季空调室外计算参数下,新风机组性能系数COP,TCOP和COPh分别为0.5,0.65和5.1。     

Feasibility and performance analysis of a desiccant solution regenerator using hot air

This paper investigated a desiccant solution regenerator using hot air to concentrate diluted desiccant solution, aiming to utilize the waste heat of hot air, such as the hot air from the condensers of vapor compression refrigeration systems. To verify the feasibility of the utilization of the hot air for the desiccant solution regeneration and disclose the performance of such kind of regenerators, performance analysis was conducted numerically by a validated mathematical model and parametric distribution of the air in a typical case was explored. The results showed that it was possible to use hot air for the desiccant solution regeneration when the requirement of the lowest inlet solution temperature was met and a typical case showed that the suggested hot air temperature was around 65 °C. Effects of main operation parameters on the regeneration thermal efficiency and regeneration rate were discussed and the result showed the regeneration thermal efficiency could achieve the maximum (η_{reg, max}) when the R was around 8 and lower flow rate of the desiccant could achieve higher η_{reg, max}. In addition, effects of dimensions of the regenerator on the regeneration performance were disclosed and some suggestions of design of the regenerators were introduced based on the study.