Thermal comfort assessment and energy consumption analysis of ground-source heat pump system combined with radiant heating/cooling

A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.

Operating performance of novel reverse-cycle defrosting method based on thermal energy storage for air source heat pump

To solve the fundamental problem of insufficient heat available during defrosting while ensuring the efficient and safe system operation for air-source heat pumps (ASHPs). A novel reverse-cycle defrosting (NRCD) method based on thermal energy storage to eliminate frost off the outdoor coil surface was developed. Comparative experiments using both the stand reverse cycle defrosting (SRCD) method and the NRCD method were carried out on an experimental ASHP unit with a nominal 2.5 kW heating capacity. The results indicate that during defrosting operation, using the NRCD method improves discharge and suction pressures by 0.24 MPa and 0.19 MPa, respectively, shortens defrosting duration by 60%, and reduces the defrosting energy consumption by 48.1% in the experimental environment, compared with those by the use of SRCD method. Therefore, using the NRCD method can shorten the defrosting duration, improve the indoor thermal comfort, and reduce the defrosting energy consumption in defrosting.

An Analytical Model for the Thermal Assessment of a Vertical Double U-Tube Ground-Coupled Heat Pump System in Steady-State Conditions

An analytical model was built to predict the thermal resistance of a vertical double U-tube ground-coupled heat pump that operates under steady-state conditions.It included a geometry obstruction factor for heat transfer throughout the backfill medium due to the presence of the second loop.The verification of the model was achieved by the implementation of five different borehole configurations and a comparison with other correlations in the available literature.The model considered a U-tube spacing range between(2)and(4)times the U-tube outside diameter producing a geometry configuration factor range of(0.29-0.6).The results of the model were utilized for the assessment of the DX ground heat exchanger coupled heat pump system.For similar geometrical configurations,the borehole thermal resistance experienced a decrease as the geometry factor increased.The single U-tube borehole thermal resistance was higher than that of the double U-tube heat exchanger by(10-27)%for the examined geometry configurations.The borehole thermal resistance at tube spacing of twice the tube diameter was higher than the predicted value at the triple diameter and fell in the range of(18-34)%.

Research on Operation of Electrothermal Integrated Energy System Including Heat Pump and Thermal Storage Units Based on Capacity Planning

In view of the Three North areas existing wind power absorption and environment pollution problems,the previous scholars have improved the wind abandon problem by adding electrothermal coupling equipment or optimizing power grid operation.In this paper,an electrothermal integrated energy system including heat pump and thermal storage units was proposed.The scheduling model was based on the load data and the output characteristics of power units,each power unit capacity was programmed without constraints,and the proposed scheduling model was compared with the traditional combined heat and power scheduling model.Results showed that the investment and pollutant discharge of the system was reduced respectively.Wind power was fully absorbed.Compared with the traditional thermal power unit,the proportion of the output was significantly decreased by the proposed model.The proposed system could provide a new prospect for wind power absorption and environment protection.

Research on single hole heat transfer power of ground source heat pump system

In this paper,the single hole heat transfer power of the ground source heat pump system in Hengshui is compared with data gained from thermal response test.The results show that maximum monitoring data of heat transfer power per meter in summer is 97.1% of the test data,and the average value accounts for 81.8%.The per meter heat power data through on-site thermal response test can provide references for designing engineering project and optimizing ground source heat pump system as these data do not vary greatly from the actual monitoring data.

Thermal Response Test by Improved Test Rig with Heating or Cooling Soil

An improved test rig providing both the heat and cold source was used to perform thermal response test （TRT）, and the line source model was used for data analysis. The principle of determining the temperature difference between the inlet and outlet of test well can keep the heating or cooling rate constant, along with a reduced size of test rig. Among the influencial factors of the line source model, the temperature difference was determined as the most important, which agreed with the test results. When the gravel was taken as the backfill material, the soil thermal conductivities of heating and cooling at the test place were 1.883 W/（m＆#183;K） and 1.754 W/（m＆#183;K）, respectively, and the deviation of TRT between heating and cooling soil was 6.8%. In the case of fine sand, the thermal conductivities of heating and cooling were 1.541 W/（m＆#183;K） and 1.486 W/（m＆#183;K）, respectively, and the corresponding deviation was 6%. It was also concluded that different velocities of water had less influence on TRT than the temperature difference.

Thermal Radiation, Joule Heating, and Viscous Dissipation Effects on MHD Forced Convection Flow with Uniform Surface Temperature

In this paper, we studied the effects of thermal radiation, Joule heating and viscous dissipation on forced convection flow in a magnetohydrodynamics (namely MHD) pump in rectangular channel with uniform surface temperature. Numerical results were obtained by solving the nonlinear governing momentum and energy equations with steady state fully developed assumptions by finite difference method. The Lorentz force in momentum and Joule heating, and viscous dissipation in energy equation with the Rossel and approximation are assumed to increase the knowledge of the details of the temperature and flow field in order to design a MHD pump. The purpose of this study is the parametric study of a Newtonian fluid in a MHD pump. The values of maximum velocity, fully developed Nusselt number for different values of magnetic density flux, Brinkman number, viscous heating and radiation number are obtained. However, the maximum temperature stays almost constant with magnetic field, as current increases, the velocity and the temperature increase too. Besides, the increase of thermal radiation number causes the increase in effective thermal conductivity and decrease in thermal boundary layer and the Nusselt number at wall.

Performance analysis of a novel tobacco-curing system with a solar-assisted heat pump

A novel tobacco-curing system with a solar-assisted heat pump was proposed.The proposed system has various advantages,such as reducing energy consumption and pollutant emissions and enhancing the stability of system operation.The thermal characteristics of the system under different climate conditions were analyzed,and the economic and environmental benefits of different tobacco-curing technologies were compared.Results indicated that the dehydration rate,the mass flux of exhaust air,and the heat load of the novel tobacco-curing system in different months had similar changes with the baking time,and all reached the maximum in the later stage of color fixing.Compared with the power saving rate of a heat pump tobacco-curing system,that of the novel system reached 25.9%-35.1%.The dry leaf curing cost of the novel system was only 0.86-1.06 yuan/kg,which can reduce the cost by more than 60%compared with traditional coal-burning tobacco-curing systems in China.Compared with other parts of the tobacco leaf,the top leaf had the lowest dry leaf curing cost due to its highest mass of dry leaf.The payback period and the annual CO_(2) emission reduction of the novel system were 3.0-3.7 a and 15586 kg,respectively.

Possibilities of Reducing Energy Consumption by Optimization of Ground Source Heat Pump Systems in Babylon, Iraq

Iraq is located in the Middle East with an area that reaches 437,072 km2 and a population of about 36 million. This country is suffering from severe electricity shortage problems which are expected to increase with time. In this research, an attempt is made to minimize this problem by combining the borehole thermal energy storage (BTES) with a heat pump, the indoor temperature of a residential building or other facility may be increased or reduced beyond the temperature interval of the heat carrier fluid. Due to the relatively high ground temperature in Middle Eastern countries, the seasonal thermal energy storages (STES) and ground source heat pump (GSHP) systems have a remarkable potential, partly because the reduced thermal losses from the underground storage and the expected high COP (ratio of thermal energy gain to required driving energy (electricity)) of a heat pump, partly because of the potential for using STES directly for heating and cooling. In this research, groundwater conditions of Babylon city in Iraq were investigated to evaluate the possibility of using GSHP to reduce energy consumption. It is believed that such system will reduce consumed energy by about 60%.

光伏光热联合双源热泵系统运行模式研究(1):最佳切换模式验证

讨论了光伏光热联合双源热泵系统制热运行的最佳切换模式。利用TRNSYS软件建立了仿真模型,对双源(水源、空气源)热泵系统性能系数(COP_(s))进行了计算,提出以某时刻空气源热泵模式或水源热泵模式运行COP_(s)较大者优先运行作为COP_(s)切换模式。通过前期实验结果验证了模拟结果的正确性,并与常规的集热水箱温度切换模式进行了对比实验,验证了COP_(s)切换模式的有效性。结果表明,该实验系统以COP_(s)最佳切换模式运行时发电量和发电效率较集热水箱温度切换模式分别提高了5.35%和1.73%,耗电量降低了17.03%,COP_(s)提高了4.91%。

光伏光热联合双源热泵系统运行模式研究(2):供暖季系统仿真研究

使用TRNSYS软件建立了光伏光热-双源热泵(PV/T-DSHP)系统的仿真模型。选取夏热冬冷地区某一近零能耗居住建筑作为研究对象,模拟研究了供暖季PV/T-DSHP系统在COP_(s)切换模式下的运行特性和能耗。结果表明:平均光电效率为15.08%,平均光热效率为33.05%;水源热泵运行模式下供暖季平均COP为4.55,空气源热泵运行模式下供暖季平均COP为3.19,PV/T-DSHP系统的平均COP_(s)为2.98;供暖季系统自满足率为61%。

基于恒热流法和恒温法的岩土热物性试验分析研究

目前岩土热物性测试仪采用的方法包括两种:恒热流法和恒温法,通过介绍两种测试方法的区别及模型算法,以北京市某公建项目岩土热物性测试结果为基准,利用TRNSYS软件分别模拟了恒热流法和恒温法的测试工况,针对模拟结果展开分析研究。经对比,试验时间至48 h时,两种测试方法利用软件模拟出的延米换热量与现场测试结果的误差在10%以内,表明若已知项目周边的地层热物性参数如地层的导热系数、热扩散率等,可将软件模拟结果作为前期地埋管系统设计的依据,并作为后续热物性勘察结果验证的参考数据。此外,根据模拟结果,由于夏季地埋管流体在设计工况下与土壤的温差值较大,为了使流体尽快达到设计工况点,恒温法测试时应选用较大的功率,否则48 h内的测试值结果与实际值偏差较大。

太阳能空气源热泵耦合相变蓄热器供热系统模拟研究

目的为提高可再生能源利用率,研究太阳能空气源热泵耦合相变蓄热器供热系统实际性能,建立适合夏热冬冷地区民用住宅的节能供热系统。方法利用TRNSYS软件建立太阳能空气源热泵耦合相变蓄热器供热系统模型,并与太阳能空气源热泵供热系统进行对比分析,对两个系统从制热量、耗电量、能效比以及室内人体热舒适度四个方面进行模拟分析,使用PMV-PPD评价方法对两个系统的室内热舒适度进行评价。结果耦合相变蓄热器的供热系统耗电量低于无相变供热系统,节能率提高了13.29%;耦合相变蓄热器的供热系统平均能效比为3.5,太阳能空气源热泵供热系统的平均能效比为3.32,提高了5.14%;耦合供热系统可以为人体提供I级室内热环境水平的热舒适度,无相变供热系统只能为人体提供II级。结论太阳能空气源热泵耦合相变蓄热器供热系统节能性更好,系统能效更高,提高了可再生能源利用率,并且耦合供热系统在热舒适性方面优于无相变供热系统。

相变储热技术在空气源热泵供暖中的应用研究现状

空气源热泵技术因具有节能、环保、高效等优点,在我国建筑供暖领域得到了广泛应用。文章分析了空气源热泵系统在供暖过程中存在的问题,介绍了利用相变储热技术优化空气源热泵运行性能的基本方式及原理。通过分析相变材料自身热物性以及相变储热单元在系统中的应用,从材料及系统两方面简述了相变储热技术在空气源热泵供暖中的研究现状及进展。最后,得出结论并针对相变储热技术在空气源热泵供暖中的应用难点,对未来发展进行了展望。

“两抽两灌”水源热泵系统应用效果分析及优化布置

为探究丹东市某工程地下水源热泵系统的实际应用效果及布井方式的合理性,采用COMSOL Multiphysics软件,建立三维水热耦合数值模型,对“两抽两灌”水源热泵系统进行为时一年的运行水温监测,并对实际应用中抽灌井的布置方式以及抽灌井间距是否存在含水层“热贯通”问题进行分析,将存在的问题与工程场地条件相结合。结果表明,采用“抽灌井平行布置”时,且抽灌井间距离为55 m时,发生“热贯通”的程度最轻,为丹东市水源热泵规划提供科学设计方法及参考依据。

基于TRNSYS的太阳能-热水源热泵复合供暖系统运行优化

针对太阳能供暖技术与热泵供暖技术的不足,提出了一种太阳能-热水源热泵复合供暖系统,并以西藏日喀则地区某项目为研究对象,利用TRNSYS仿真模拟软件建立太阳能-热水源热泵复合供暖系统模型,模拟分析该供暖系统的运行特性,并对系统的经济性进行了分析,然后利用Hooke-Jeeves优化算法对供暖系统关键参数进行优化。结果表明:西藏地区太阳能-热水源热泵复合供暖系统能够高效稳定运行,实现了对太阳能由高温到低温的梯级利用,供暖季系统季节能效比可达4.43;相比于电锅炉供暖,复合供暖系统具有更高的经济性,静态回收期为5.3年;优化后系统能耗减少,供暖季系统季节能效比提高了7.9%。

光伏光热-双源热泵系统地区适用性研究

利用TRNSYS软件建立了光伏光热-双源热泵(PV/T-DSHP)系统仿真模型,选取拉萨和上海对PV/T-DSHP系统的运行特性进行了模拟分析,对不同室外气象条件(环境温度、太阳辐照度)下单一光伏-空气源热泵(PV-ASHP)系统和光伏光热-水源热泵(PV/T-WSHP)系统的性能系数进行了对比分析。结果表明:PV/T-DSHP系统在拉萨和上海的供暖季平均系统性能系数(COP s)分别为4.23和3.34;在太阳能资源一般区和丰富区,PV/T-WSHP系统较PV-ASHP系统在根据环境温度和太阳辐照度划定的最佳COP*s运行区域内运行更具性能优势。

基于蓄热装置辅助的燃料电池电动车供暖系统动态仿真

为了辅助燃料电池车辆预热,提升燃料电池在低温下的冷启动速率以及降低电动车能耗,该文提出了一种基于热泵和蓄热装置联合的燃料电池电动车供暖方案,并开展了燃料电池车辆系统动态仿真研究,对比了有无蓄热装置辅助的系统对车辆运行过程的影响。结果表明:在寒冷运行环境下,蓄热装置可确保驾驶循环工况下循环冷却液热量来源的连续性,相较于无蓄热装置的热管理系统,热泵和蓄热联合供暖方案可使空调系统能耗下降26%;利用蓄热装置辅助的供暖系统能够改善燃料电池电动车的冬季冷启动特性,优化车辆电池系统的热管理。

竖直单U型地埋管换热器埋管间负热阻现象的参数化研究与分析

基于Mutipole方法对竖直单U型地埋管换热器钻孔内外的耦合传热过程进行求解,在钻孔内三热阻和四热阻简化传热模型基础上,详细地分析钻孔内的复杂稳态传热过程,参数化研究埋管布置结构、回填料与岩土热物性等因素对钻孔内埋管间直接传热热阻的影响规律,揭示导致钻孔内埋管间负热阻现象的本质原因,对钻孔内热阻传热模型的工程实践应用给出参考意见。

竖进平出型地埋管群换热器结构与控制优化

【目的】为提高浅层地热能利用效率,亟须对影响地源热泵系统性能的地埋管换热器结构和控制开展优化设计。【方法】建立了一种竖进平出型地埋管群换热器模型,研究其换热系统性能,探究其最佳结构及运行方式。【结果】管群布置横纵比越低,单位面积换热量越大,横纵比超过0.15后对系统影响较小;换热器间距越小,土壤利用率越高,但热短路损失越大;双列双出型埋管每延米换热量相较于双列单出型结构提升7%以上;负荷较大工况下叉排布置结构的换热效果更好;整个夏季优化结构的平均出口温度下降2.28℃,换热器周围土壤温度下降1℃以上;实际运行过程中应优先考虑采用流速随负荷变化控制模式。【结论】研究结果可为地源热泵换热器的设计、制造提供理论依据。