太阳能电池与热泵热水器联合运行系统性能分析

为了降低太阳能光伏电池的温度,同时提升热泵热水器的蒸发温度,利用循环水路冷却太阳能光伏电池,并将热量传递给热泵热水器的蒸发器,构成联合运行系统。针对杭州市的夏季和冬季气象条件,对该联合运行系统的性能进行了计算,分析了对应不同太阳能电池温度下的系统运行参数的变化情况,包括太阳能电池发电效率和所需换热量,热泵热水器的制热量以及热泵效率等。计算结果表明,该联合运行系统能够同时提高太阳能电池光伏转换效率和热泵效率。     

一种新型太阳能辅助高温热泵系统性能分析

为降低压缩机排气温度、优化热泵系统性能,设计了 一种利用太阳能集热器加热压缩机排气,利用蒸气显热制取高温热水的新型太阳能辅助热泵系统.结合天津地区的辐射日照条件对新型太阳能辅助热泵系统进行了可行性和热力性能分析,并将其与直膨式太阳能辅助热泵系统的性能进行对比.结果表明:该系统通过提高蒸发温度,可以降低制冷压缩机排气温度...     

太阳能热泵的性能分析

分析了工作温度对太阳能集热器和热泵的影响:降低太阳能集热器的集热温度和提高热泵的蒸发温度,有利于改善太阳能热泵系统的工作性能;设定了太阳能热泵的一些参数,计算和说明其性能;指出了太阳能热利用技术与热泵技术的有机结合,是解决"全天候工作"和"太阳能建筑一体化"问题的有效方式.     

直膨式太阳能热泵制热性能的对比研究

直膨式太阳能热泵(direct expansion solar assisted heat pump,DX-SAHP)可直接吸收利用太阳能,进而提高热泵的蒸发温度和性能系数(COP),有利于改善热泵的热性能和结霜。本文在带有太阳模拟发射器的焓差实验室中建立直膨式太阳能热泵和常规直彭热泵的对比实验,对不同条件下的热泵系统参数进行测量并进行性能对比和分析。实验结果显示,直膨式太阳能热泵能够吸收太阳能,在辐照度分别为100和200 W/m~2的工况下,系统制热功率比无辐照时的制热功率分别提高9.8%和21.8%,COP分别提高11.7%和23.7%,且除霜启动延迟23 min;辐照度为200 W/m~2时,直膨式太阳能热泵在环境温度5℃下的制热功率比1℃下的制热功率提高16.92%;在室外温度为1℃,相对湿度为95%的工况下,提高太阳辐照度,可有效减小涂层蒸发器进出口温度的波动,提高蒸发器运行的稳定性。此外,直膨式太阳能热泵在运行过程中吸收的太阳辐射被用来蒸发液态制冷剂工质,导致压缩机进气量增加,系统的制热功率和COP提高。     

间接膨胀式太阳能高温热泵系统运行性能实验研究

为研究间接膨胀式太阳能高温热泵系统实际应用的可行性和有效性,搭建实验平台,在天津地区气象条件下对高温热泵全天动态运行特性开展实验研究,分析太阳辐射强度、水箱储热性能、冷凝温度及膨胀阀开度对系统运行性能影响。结果表明:平均太阳辐射强度由396 W/m2增加到563 W/m2,高温热泵性能系数COP由3.62增至3.93;因水箱储热功能,间接膨胀式系统在太阳辐射强度剧烈波动时能够保持高温热泵相对稳定的蒸发温度;当蒸发温度固定时高温热泵COP随冷凝温度升高而降低,冷凝温度由70 ℃增至80 ℃,COP由4.32降至2.76;膨胀阀开度由150步增至250步,高温热泵全天平均COP由3.14升至5.12,排气压力降低46%。     

相变储能太阳能热泵系统的试验研究

文章建立了相变储能太阳能热泵系统试验平台,介绍了系统的运行方式以及各个部分的运行原理,选取典型日进行试验,并对试验数据进行分析。分析结果表明:相变储能太阳能热泵系统能够满足北方农村的供暖需求,可以保证白天室内的温度达到22℃,COP的最大值为6.3;太阳能热泵系统停止工作后,相变储能箱可以保证室内温度达到供暖的需求温度7 h,起到了"削峰填谷"的作用,运行费用显著降低;相变储能太阳能热泵系统解决了单纯电加热供暖方式费用高、能耗高的问题,具有显著的节能性。     

太阳能辅助二氧化碳热泵热水系统实验研究

利用实验的方法,研究了太阳辐照度、外界气温和风速、初始水温、蒸发器出口温度和压力等对太阳能辅助二氧化碳热泵热水系统运行状况和COP的影响。实验结果表明,系统COP随初始水温的升高而增大;太阳辐照度、外界温度和风速对热泵系统性能的影响主要体现在对系统循环水温的影响;在一定范围内,蒸发压力和蒸发温度越高,热泵系统的COP越大。     

发生温度对太阳能喷射式制冷系统性能的影响研究

为了确定发生温度对太阳能喷射式制冷系统性能的影响,基于太阳能喷射式制冷系统试验台,以蒸发温度、冷凝温度及室内环境温度为定量,发生温度为变量进行了试验研究.试验结果表明:当喷射器结构确定时,喷射系数ER、系统性能系数COP和机械性能系数COP_m均不会随着发生温度的升高一直增大,系统必然存在一个最佳的发生温度使其性能达到最佳.研究可为今后最佳发生温度的选择及实际应用中如何维持系统高效运行提供理论指导.     

太阳能-空气源热泵联合干燥系统设计及干燥枸杞的实验研究

为缩短枸杞干燥时间,提高干制枸杞的质量,减少能源消耗,本文提出了一种新型太阳能–空气源热泵联合干燥系统。该系统主要由太阳能集热器和空气源热泵机组等设备组成,可以实现太阳能单独干燥、热泵单独干燥和太阳能–空气源热泵联合干燥三种工作模式。本文根据枸杞的干燥特性,分段设定最佳的干燥温度,进行了热泵单独运行和太阳能–热泵联合运行两种工作模式下干燥枸杞的对比实验。结果表明,干燥50 kg枸杞,太阳能–热泵联合运行比热泵单独运行节省了2.9 kW?h电能,若同时除去系统本身的耗能,节省的电能占热泵单独运行耗电量的29.5%。同时,与太阳能单独干燥相比,太阳能–热泵联合干燥具有较高的除湿能耗比,两者最大差值为0.71 kg/(kW?h)。本文提出的太阳能–热泵联合干燥系统具有提高干燥产品的品质、缩短干燥时间和节约干燥成本等优点,适宜推广。     

太阳能对热泵循环性能的影响

利用太阳能-土壤源复合热泵实验平台进行太阳能热泵运行实验,分析提高蒸发器进口水温对热泵性能的影响。实验结果表明:随着蒸发器进口水温的升高,热泵吸热量和制热量增速较大,输入功率增速较小,因而机组COP和系统COP也随之升高。压缩机排气压力和吸气压力也随之升高,但排气压力的增速小于吸气压力的增速,压缩比逐渐减低。提高蒸发器进口水温可以提高蒸发温度,进而明显改善热泵的性能状态。     

Experimental Analysis of a Solar Energy Storage Heat Pump System

This paper introduces a novel solar-assisted heat pump system with phase change energy storage and describes the methodology used to analyze the performance of the proposed system. A mathematical model was established for the key parts of the system including solar evaporator, condenser, phase change energy storage tank, and compressor. In parallel to the modelling work, an experimental set-up of the proposed solar energy storage heat pump system was developed. The experimental data showed that the designed system is capable of meeting cold day heating demands in rural areas of Yanbian city located in Jilin province of China. In day-time operation, the solar heat pump system stores excess energy in the energy storage tank for heating purposes. A desired indoor temperature was achieved; the average coefficient of performance of solar heat pump was identified as 4.5, and the system showed a stable performance throughout the day. In night-time operation, the energy stored in the storage tank was released through a liquid-solid change of phase in the employed phase-change material. In this way, the provision of continuous heat for ten hours was ensured within the building, and the desired indoor air conditions were achieved.     

Experimental study on the performance of solar-assisted multi-functional heat pump based on enthalpy difference lab with solar simulator

In the enthalpy difference lab with a solar simulator, the performance of the indirect expansion solar-assisted multi-functional heat pump (IX-SAMHP) can be tested in stable external environment quantificationally. In this paper, the performances of the IX-SAMHP working in the solar water heating mode and solar space heating mode were compared under different conditions. The experimental results indicate that the evaporating heat exchange rate and condensing heat exchange rate were synthetically effected by the evaporating and condensing temperature in the solar water heating mode. Moreover, compared with the situation without irradiation, when the irradiation was 500 W/m², the evaporating heat exchange rate and condensing heat exchange rate increased by 37.4% and 32.3%, respectively. In the solar space heating mode, when the irradiation increased from 0 W/m² to 500 W/m², the heating capacity increased by 20.4%. In the second-law analysis, the calculating results demonstrate that the exergy efficiency of the IX-SAMHP would be enhanced by inputting solar energy to the evaporator.     

Performance of ejector heat pumps

An ejector-compression heat pump can use low-grade thermal energy in the neighbourhood of 93.3°C (200°F) to provide space cooling and heating. This paper applies the existing ejector theory to estimate the performance of an ejector heat pump system at various operating conditions. The study includes parametric, sensitivity and off-design analyses of the heat pump performance. The performance enhancement options and desired ejector geometry are also examined. Refrigerants 11, 113 and 114 are three of the halocarbons most suitable for the ejector heat pump system. The estimated coefficients of performance for a simple ejector heat pump are 0.3 for the cooling mode and 1.3 for the heating mode at a sample operating condition in which the refrigerant (R-11) boiling temperature is 93.3°C (200°F), condensing temperature 43.3°C (110°F) and evaporating temperature 10°C (50°F). A 24 per cent performance improvement is predicted for a heat pump with two-stage ejectors and regenerative heat exchangers. The off-design performance is relatively insensitive to the evaporator temperature variations.     

Performance study of a photovoltaic solar assisted heat pump with variable-frequency compressor – A case study in Tibet

The performance of a photovoltaic solar assisted heat pump (PV-SAHP) with variable-frequency compressor is reported in this paper. The system is a direct integration of photovoltaic/thermal solar collectors and heat pump. The solar collectors extract the required thermal energy from the heat pump and at the same time, the cooling effect of the refrigerant lowers the working temperature of the solar cells. So this combined system has a relatively high thermal performance with an improved photovoltaic efficiency. To adapt to the continuously changing solar radiation and ambient temperature conditions, the refrigerant mass flow rate should match the heat gain at the evaporator accordingly. A variable-frequency compressor and an electricity-operated expansion valve were used in the proposed system. Mathematical models were developed to evaluate the energy performance of the combined system based on the weather conditions of Tibet. The simulation results indicated that on a typical sunny winter day with light breeze, the average COP could reach 6.01, and the average electricity efficiency, thermal efficiency and overall efficiency were 0.135, 0.479 and 0.625 respectively.     

太阳能与热泵联合干燥木材的优化匹配

介绍了太阳能与热泵联合干燥系统的组成与工作原理.通过理论分析与实验研究探讨了太阳能与热泵联合运行的优化匹配,当太阳能供热量能满足木材干燥所需热量时,由太阳能系统供热;否则由太阳能与热采联合供热;阴雨天和夜间由热泵供热.当太阳能送风温度低,但高于环境温度时,低温太阳能向热泵送风,可以提高热泵的供热系数和供热量.对应于一定的环境温度,太阳能向热泵送风有一个相匹配的最低温差.例如当环境温度为24℃时,通过理论和实验求得太阳能向热泵送风与环境温度间的最低送风温差分别为4℃和6℃.     

A computational model of a domestic solar heating system with underground spherical thermal storage

This theoretical study deals with a domestic heating system assisted by solar energy stored in an underground spherical container. The system includes a heat pump. The analytical model employed calculates the water temperature in the storage vessel, as well as the temperature distribution in the surrounding geological structure, by using the monthly-average solar radiation and ambient temperature. Storage temperature, collector efficiency, performance coefficient of the heat pump (COP) and annual solar fraction are computed and presented in various graphs. The importance of seasonal solar energy storing in the ground is demonstrated.     

A solar pond-assisted heat pump for greenhouses

A solar pond for annual cycle solar energy collection and storage was studied at The Ohio Agricultural Research and Development Center (OARDC), Wooster. It has been used as a thermal energy source for greenhouse heating. A brine-source electric-power-driven heat pump was incorporated into the heat extraction system. Initial results of the field studies indicated that the combined system improved the effectiveness of both the heat pump and the solar pond by enabling a larger temperature cycle within the solar pond.

To study the operation of such a system, a computer simulation model for the heating system was developed. The results of simulations were used to establish a relationship between the system performance and the present design and for sizing the solar energy collection and storage system. Also, the effect of a polystyrene pellet nighttime insulation for the greenhouse was simulated. Increasing the surface area of the OARDC pond was found to be less effective than changing its depth. Thr results showed that a 5 m deep pond with 1.0 m gradient zone significantly improved the overall performance of the system when used as a heat source for a heat pump. Based on the detailed experimental and computer simulation performance analysis, the solar pond-assisted heat pump system has the potential of improved performance compared with convential air source heat pumps.     

Numerical simulation and experimental validation of indirect expansion solar-assisted multi-functional heat pump

A novel indirect expansion solar-assisted multi-functional heat pump (IX-SAMHP) system which composes of the multi-functional heat pump system and solar thermal collecting system is proposed and studied in this paper. This system can fulfill space heating, space cooling and water heating with high energy efficiency by utilizing solar energy. For solar water heating mode and solar space heating mode, a dynamic model is presented and validated with the experimental results. The simulation results show good consistency with the experimental data, and the established model is able to predict the system performance at a reasonable accuracy (with the root mean square deviations less than 5%). On this basis, the performances of the IX-SAMHP system are investigated under different parametric conditions. For solar water heating mode, simultaneously operating the solar thermal collecting system and multi-functional heat pump system can be an energy efficiency method. With the solar irradiation rising from 0W/m² to 800W/m², the COP increases from 2.35 to 2.57. In solar space heating mode, the effect of the mass flow rate of water in evaporator is investigated. To balance the heating capacity and COP, the mass flow rate of water should be adjusted according to different temperature demands and heat load.     

太阳能热泵供热系统实验台的设计及误差分析

开发新能源和节能是寻找能源出路的两大途径,太阳能热泵系统以其显著的节能性和环保性具有广阔的发展前景。介绍了太阳能热泵供热实验台集热器、蓄热器等设备的设计,分析了集热器集热效率的测试误差,指出太阳能热泵供热实验台测试数据准确、可靠,为太阳能热泵供热系统的设计、安装和运行提供了有价值的参考依据。