The Characteristics of the Evaporator/Evaporator for Direct Expansion Solar Assisted Heat Pump System

Direct expansion solar assisted heat pump (DX-SAHP) technology is developed by combining solar energy heat utilization with heat pump energy saving technology. The experimental researches of the DX-SAHP hot water system are conducted in this paper, and overall performance of DX-SAHP is analyzed with three different structures of collectors/evaporators, namely a bare-plate collector, a glass-plate collector and double collectors/evaporators (a bare-plate collector and a glass-plate collector). The influence factors and overall performance are studied, which show that the overall performance of the system is mainly influenced by solar irradiation intensity and the collector area. Comparing with glass-plate collector in similar conditions, bare-plate collector system COP is higher. While increasing collector area is conducive to improve the system COP, but will reduce the collector efficiency and increase the workload of the compressor by comparing the bare-plate collector with double-plate collectors.

Comprehensive Benefit Analysis of Direct Expansion Ground Source Heat Pump System

Direct Expansion Ground Source Heat Pump (DXGSHP) system directly extracts heat or cold energy from ground by consuming electricity to provide for space conditioning. Compared with the currently widely-used secondary loop Ground Couple Heat Pump (GCHP) system, it has higher energy efficiency, lower operating costs, and less environmental impact. A case study is carried out in this paper. The subject is a residential building located in Beijing, China. It is assumed that the building adopts the DXGSHP system and the GCHP system respectively. Annual loads and energy consumption are simulated and computed. Then the initial cost, operating cost and CO2 emission are calculated. The economic benefit is analyzed with the Payback Time method and the Dynamic Annual Cost Value method. The environmental benefit is discussed mainly by comparing the CO2 emission savings. The results show that the DXGSHP system has higher initial costs, but lower operating costs, and less greenhouse gas emissions. The DXGSHP system has better comprehensive benefits than the GCHP system.

Analysis of Thermodynamic Characteristic Changes in Direct Expansion Ground Source Heat Pump Using Hydrofluoroolefins (HFOs) Substituting for HFC-134a

HFO-1234yf and HFO-1234ze[E] have low global warming potential and zero ozone depletion potential. If they are used in the direct expansion ground source heat pump system substituting for HFC-134a, the system will be beneficial to mitigating climate change. This study aims to find out the thermodynamic characteristics of the direct expansion ground source heat pump system using HFO-1234yf or HFO-1234ze[E] by theoretical calculation. The results indicate that HFO-1234yf system in an actual cycle has the highest COP. HFO-1234yf and HFO-1234ze[E] have such smaller capacity per unit of swept volume that they need larger compression capacity if providing the same heating or cooling loads. For a given unit when HFC-134a is replaced with HFO-1234yf or HFO-1234ze[E], the capacity will decrease. More refrigerant charge is required in the HFO-1234yf or HFO-1234ze[E] system. The results also present that more refrigerant charge is required in the cooling mode than in the heating mode.

Simulation of embedded heat exchangers of solar aided ground source heat pump system

Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 ℃ higher than the original one after one year's running. It is beneficial for the system to operate for long period.

Exergy Analysis of Direct-Expansion Solar-Assisted Heat Pump Based on Experimental Data

The purpose of this research is to reveal the exergy variation of each component in a direct-expansion solar-assisted heat pump(DX-SAHP)system.Exergy analysis of the DX-SAHP system with R134a is conducted.and the performance evaluation is done.The proposed system is mainly composed of a bare plate solar collec-tor/evaporator,a hermetic variable-frequency rotary-type compressor,a micro-channel condenser and an electronic expansion valve.The experimental data include the exergy loss rates.irreversibility rates and exergy loss ratios of all components and the infuences of ambient temperature on these parameters.The analysis results show that the average irreversibility rate of the compressor is 204.8 W at an ambient temperature of 16℃,and 149.9 W atan ambient temperature of 27℃.The highest irreversibility rate occurs in the compression process,followed by the throttling process.the evaporation process and the condensation process.

太阳能PV/T+相变能与直蒸式水源热泵供热(冷)系统特性分析

为解决河北农村建筑清洁供暖问题和太阳能利用具有不稳定性问题,设计了太阳能PV/T+相变能与直蒸式水源热泵供热(冷)系统进行实验研究。实验结果表明,冬季典型日系统发电量为4.453kWh,制热系数COP平均值3.41;夏季典型日系统发电量为5.945kWh,制冷系数EER平均值3.2;将发电量用于系统运行,制热系数COP为4.22,制冷系数EER为4.19,分别提高了23.75%和30.12%;夏季单纯PV/T太阳能电池发电量5.537kWh,本系统的发电量提高了7.37%。该系统经济效益高,运行稳定,是一种实现河北农村清洁供暖有效途径。

智能技术在直膨式太阳能热泵效能优化中的应用

阐述人工智能驱动下的直膨式太阳能热泵系统在效能提升方面的应用和成果。通过人工智能在系统中的应用,实现对太阳能资源的监测和预测、控制算法、能耗优化和协调管理的改进。

A Numerical Model of a U-Tube Vertical Ground Heat Exchanger Used as an Evaporator

The paper presents a general distributed model of a vertical U-tube direct expansion heat exchanger coupled with the ground. This model is developed for studying the dynamic thermal behavior of a buried heat exchanger which is an integral part of a so-called direct expansion heat pump. The transient conservative equations of mass, momentum and energy considering single and two-phase flow of refrigerant are derived and presented. The diffusive heat exchange with the ground is treated using an analytical approach to treat short-time scale response of vertical boreholes based on an imposed temperature. The thermal interference between the two pipes of the heat exchanger is also considered. The mathematical equations of the model are numerically presented using a control volume formulation and the solution of the system of equations is obtained by successive iterations. The dynamic behavior of the evaporator is simulated and the numerical results are analyzed regarding spatial parameters distribution and thermal interference influence.

直膨式太阳能PVT热泵热水系统运行性能仿真与分析

直膨式太阳能光伏光热(photovoltaic-thermal,PVT)热泵是一种综合利用太阳能资源的新型高效技术。为探究不同环境条件以及系统配置方式对直膨式太阳能PVT热泵热水系统运行性能的影响,基于能量平衡原理在Matlab平台上建立了系统的仿真模型,基于临港地区的环境数据,分析了各季节典型日下不同配置系统的热水供应性能以及发电增益的全年波动情况。结果表明,随压缩机理论输气量的减小,热水系统的性能系数(coefficient of performance,COP)有所提高,但所需的加热时间增加,系统的全年发电增益随理论输气量的减小而减小。

太阳能直驱直储耦合地源热泵系统运行分析研究

针对严寒地区建筑采用传统地源热泵系统会造成土壤温度逐年下降的问题,本文提出一种太阳能直驱直储耦合地源热泵系统,基于TRNSYS建立系统仿真模型,探究长期运行下系统性能变化趋势。结果表明:系统运行一年后储热管群和换热管群土壤温度分别升高1.6℃和0.4℃,改善了严寒地区土壤温度低的问题。运行5年后机组COP和系统COP分别达到了3.87和3.56,分别较系统运行第一年提高9%和8%。

太阳能热泵系统配置形式及其研究进展

采用不同用途及配置形式相结合的分类方法对太阳能热泵系统进行分类,指出不同形式太阳能热泵系统的特点、当前研究现状及未来发展趋势,分析环境及运行参数对系统热力性能的影响。通过文献综述发现,在一定运行工况下,直膨式太阳能热泵系统性能系数(COP)值可达9.40以上,非直膨式太阳能热泵系统COP值可达8.80以上。提出太阳能热泵系统的应用与研究应从能耗与效率、经济性、可靠性、运行与操控等方面着手,朝更加高效经济、节能可靠的方向发展。

不同地区太阳能PVT热泵系统仿真模拟与运行性能分析

为探究环境条件的时空分布差异性对太阳能直膨式光伏光热(PVT)热泵系统运行性能的影响,进行数学建模与性能仿真,分析了系统在不同地区采暖季内的运行性能。结果表明:由于入射太阳辐射的效应,在不同地区,系统的采暖季平均蒸发温度都提高至接近甚至超过环境温度的水平,显著改善了系统的热力性能;当冷凝温度为50℃时,系统在北京、拉萨、兰州的采暖季平均COP分别为3.67、5.01和3.41;采暖季平均单板得热功率分别为541 W、810 W和504 W,得热因子分别为71.7%、62.0%和79.3%,光伏发电增益分别为4.76%、8.67%和6.10%。

严寒地区太阳能跨季节蓄热热泵系统研究

针对我国严寒地区冬季热负荷远大于夏季冷负荷导致的土壤热失衡问题,选取包头市某医院为对象,应用TRNSYS仿真软件分析太阳能跨季节蓄热土壤源热泵系统的性能。分析结果表明:跨季节蓄热系统运行10年内,土壤温度由10.00℃提升到10.68℃,太阳能-土壤源热泵复合系统的土壤温度下降至5.62℃。此时跨季节蓄热模式热泵机组的性能系数为3.25,同比上涨2.20%;供冷季热泵机组的性能系数为7.55,同比上涨0.13%。同时,总耗电量相较于复合系统减少11.54%。由此可见,太阳能跨季节蓄热模式不仅可以提高土壤源热泵制热性能系数,又能有效缓解土壤热失衡的现象,同时节约系统总耗电量。

直膨式太阳能PVT热泵热水系统在不同城市运行性能仿真与分析

基于直膨式太阳能光伏光热(PVT)热泵热水系统的工作原理,根据迭代算法建立了系统的仿真模型,以探究系统在不同环境条件下的运行性能。结果表明:在上海、北京、拉萨、兰州、昆明和广州,直膨式PVT热泵热水系统在夏季典型工作日的平均COP分别为7.34、7.30、6.98、8.18、6.24和6.79,加热定量热水所需时间分别为275 min、273 min、279 min、243 min、314 min和295 min,冬季典型工作日的平均COP分别为5.59、5.21、6.05、5.03、6.48和5.43,加热定量热水所需时间分别为344 min、364 min、316 min、376 min、298 min和359 min;在上海、北京、拉萨、兰州、昆明和广州,相对于纯光伏组件,PVT组件的全年平均发电增益分别为9.28%、8.56%、10.42%、10.01%、7.70%和7.64%。

直膨式太阳能热泵供暖系统实验及性能分析

围绕建筑供暖需求,本文构建了太阳能集热/蒸发器和翅片蒸发器并联的直膨式太阳能热泵(direct expansion solar assisted heat pump,DX-SAHP)供暖系统,分析了系统热力循环过程,搭建了系统的工程应用实验平台,实验结果分析表明,DX-SAHP供暖系统在不同运行工况下可获得较高的性能,性能系数(coefficient of performance,COP)最高可达到6.88,压缩机频率、太阳辐照度和环境温度对系统的制热量和COP均有影响;压缩机定频运行时,太阳能集热/蒸发器运行的COP比翅片蒸发器大约高30%,变频运行时大约高45%,变频运行具有更优的性能。

真空管直膨式太阳能热泵系统性能分析

该文将真空管集热器与直膨式太阳能热泵结合,提出一种真空管直膨式太阳能热泵系统。实验研究典型工况下太阳辐照度、循环水温度对系统性能的影响,并探讨压缩机变频条件下系统的动态性能。结果表明,提高太阳辐照度、降低循环水温度有利于提高系统性能,在太阳辐照度为850 W/m^(2),循环水温度为55℃时系统取得最大COP,为5.36。压缩机频率为42 Hz的系统COP为4.08,较45、47、50 Hz分别提高1.23%、8.5%、13.6%。

直膨式太阳能热泵系统冬季工况性能分析

直膨式太阳能热泵系统的集热蒸发器通过吸收太阳辐射,使冬季工况下热泵的性能得到有效提高,减少了电能消耗,得到了广泛应用。通过实验测试了直膨式太阳能热泵系统冬季工况下的性能参数,讨论了单日内白天在太阳辐照下热泵性能的变化。分析发现,集热蒸发器内制冷剂进口温度随太阳辐照度迅速升高,在正午时刻之前,进口温度可由0.1℃升至10.3℃。系统过热度波动维持在约0.3℃以内之间。当进口压力达到单日内极值418.8 kPa时,系统制冷剂流量以及制冷量较初始时刻分别增加1.76 kg/h、168.2 W。系统得热量则呈现出先增后降的趋势,正午时刻达到最大得热量2 199.55 kJ。太阳辐照度由363.31 W/m^(2)变化到585.39 W/m^(2),集热蒸发器有效集热率由1.01减至0.41。日均太阳辐照度变化200 W/m^(2)时,COP由1.61升高到2.93。建立了制冷剂蒸发温度、冷凝温度与COP之间的函数关系COP_(a)=6.01-0.284ΔT0.689。

R134a应用于直接膨胀式太阳能热泵系统

利用平衡均相理论建立了太阳能集热器两相流模型 ,用四阶 Runge- Kutta方法对其求解 ,实验验证了其可靠性 .利用该模型从理论上研究了以 R1 34 a作为工质的直接膨胀式太阳能热泵的性能 ,并与采用 R1 2作为工质的结果进行比较 ,指出了 R1 34 a应用于此类热泵的适用性 .理论结果还表明 ,在较宽的环境温度、冷凝温度和太阳能辐照度范围内 ,采用 R1 34 a作为工质 ,热泵系统的性能系数可达到 4.0～ 6 .5 .

直膨式太阳能热泵热水器热力性能分析及优化设计

针对"直膨式太阳能热泵热水器"750W实验样机(系统A)进行了过渡季节运行工况下的实验研究,根据实验数据计算出系统供热性能系数、太阳集热效率和各主要部件的有效能损失系数以及系统的有效能效率等热力学指标,对各部件可加以完善的潜力做了量化分析,为整套系统的进一步优化设计提供参考。根据分析结果,研制了小型化400W实验样机(系统B)并加以实验验证。通过对比分析发现,两套系统各主要部件的有效能损失以压缩机(其有效能损失系数,系统A为40%,系统B为34%)和太阳集热/蒸发器(其有效能损失系数,系统A为21%,系统B为37%)为最大,然后依次是冷凝器(其有效能损失系数,系统A为11%,系统B为8%)和热力膨胀阀(其有效能损失系数,系统A和系统B均为5%)。因此,压缩机的合理选配、集热器的优化设计是提高太阳能热泵热水器性能的关键。

间接膨胀式太阳能多功能热泵供热实验

提出了一种太阳能与多功能热泵技术有机结合的间接膨胀式太阳能多功能热泵（IESAMDHP）系统．描述了间接膨胀式太阳能多功能热泵系统的组成及工作原理，并阐述了各种功能模式的运行条件和运行方式．重点对研制的IESA-MDHP实验样机的供热性能进行了实验研究．实验结果表明，IESA-MDHP系统的COPhp在3．30～4．71之间变化，而COPsys在2．88～3．96之间变化，明显高于传统的家用空气源热泵系统，但[火用]性能系数在0．17～0．31之间变化．