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.

Exergo-Environmental Study of a Recent Organic Solar Hybrid Heat Pump

A hybrid heat pump(compression/absorption)with an integrated thermal photovoltaic unit is studied.The considered working fluids are organic mixtures:R245fa/DMAC and R236fa/DMAC,chosen for their low Global Warming Potential.The main objective is the optimization of energy efficiency in order to minimize the environmental impact through the implementation of a sustainable strategy.It is shown that Exergy Analysis itself is a valuable tool in energy integration.Within the imposed framework of minimizing total annual costs,entropy analysis can be instrumental in determining the optimal plant concept,optimizing energy conversion and use,and improving profitability.The present results are discussed under the optimistic hope that they may help to define new energy and environmental policies.

Performance analysis of U-vertical direct-expansion ground-source heat pump

The performance of a direct-expansion ground-source heat pump（DX GSHP）system is theoretically analyzed.Compared with the conventional ground-source heat pump（GSHP）,the DX GSHP has a lower condensing temperature in the cooling mode and a higher evaporating temperature in the heating mode,and the ground heat exchanger（GHE）in the DX GSHP has a low thermal resistance.Therefore,the coefficient of performance（COP）of the DX GSHP is higher than that of the GSHP.In addition,the system performance of the DX GSHP system is higher than that of the conventional GSHP system because there are no secondary solution loops and water circulating pumps in the DX GSHP system.The experimental energy performance of the DX GSHP system is also investigated based on the actual operational data.The tested DX GSHP system is installed in Xiangtan,China.The U-vertical GHE of the DX GSHP is buried in a water well.The length and the outside nominal diameter of the GHE are 42 m and 12.7 mm,respectively.The experimental results show that the maximum（COP）and the average COP of the DX GSHP system in the heating mode are 5.95 and 4.72,respectively.

Experimental Investigation on System with Combination of Ground-Source Heat Pump and Solar Collector

This paper presents the heating performance and energy distribution of a system with the combination of ground-source heat pump and solar collector or a solar-assisted ground-source heat pump system (SAGSHPS) by calculation and experiment.The results show that the average absolute error is less than 0.6 ℃ and the relative error is less than 5% under the pulse load when the analytical solution to the 2-D solid cylindrical source model is used for the SAGSHPS.The coefficient of performance (COP) of the SAGSHPS is 2.95-4.70.The average fluid temperature in the borehole heat exchanger can increase by 3 ℃ with the assistance of solar collector,which will improve the COP of the heat pump by approximately 10% from the experimental data.The energy contributions to the total heating load of soil,electricity and solar are 56.30%,36.87% and 6.83%,respectively.

Research on Performance of Ground-Source Heat Pump Double U Underground Pipe Heat Exchange

This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.

Energy saving analysis of a hybrid ground-coupled heat pump project

A hybrid ground-coupled heat pump（HGCHP）project in Nanjing,China is chosen to analyze the building energy-consumption properties in terms of different control strategies,building envelope and the terminal air-conditioning system.The HGCHP uses a supplemental heat rejecter to dissipate extra thermal energy to guarantee underground soil heat balance.The software EnergyPlus is employed to simulate the project and design the heat flow of the cooling tower and the borehole heat exchanger（BHE）.Then two feasible control strategies for the cooling tower and the borehole heat exchanger are proposed.The energy-saving potential of the building envelope is analyzed in terms of the surface color of the wall/roof.With the same terminal system,it is found that in the cooling season the heat flow of the insulated building with black wall/roof is 1.2 times more than that with white wall/roof.With the same insulated building and gray wall/roof,it is concluded that the heat pump units for a primary air fan-coil system show an annual energy consumption increase of 44.7 GJ compared with a radiant floor system.

Mathematical model of absorption and hybrid heat pump

Recovering waste heat from industrial processes is bene ficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions.The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles.Studies about the simulations and modeling of hybrid heat pumps are few in literature.In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with Chem Cad? 6.0.1.LiBr–H_2O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results.Binary parameters of activity coef ficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions.A design of heat pumps is developed and a new modeling of generator is analyzed.The coef ficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively.For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator,the concentration of Li–Br solution on coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients of performance,the primary energy ratio,the generator heat,and the compressor power are analyzed for different values of compressor proportion.Results show that comparing the two systems the hybrid pump allows to save more primary energy,costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter.Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.

Heating and Cooling Hybrid System with Gas Mixture Sourced Heat Pump and Heating Boiler

Preliminary investigation shows that air sourced type heat pumps by energy efficiency are competitive with gas boilers having 93% of coefficient of performance （COP） if heat pumps are used in climatic zones, having outside air temperature higher than （-3 ℃ to -5 ℃）. But, in such conditions the heat pump＇s evaporator is covered by ice crust, which cuts off the flow of outside air-heat source through the evaporator of heat pump. For avoiding stating problems it is recommended to use as heat source a mixture of waste warm gases. In this article a high efficiency heating-cooling system is developed, consisting of warm gases mixture sourced heat pump, heating boiler operating simultaneously with heat pump and solar air heater. The heating demand of the served house is shared between boiler and heat pump. Instead of outside air the warm gases mixture enters into evaporator of heat pump. A new construction of heat exchanger was developed. The article presents the structure and principle of operation, as well as the method for optimization and design of suggested system. Analysis proved high energy efficiency and cost effectiveness of the new system.

Desalination by Simple Solar Distiller Assisted by a Heat Pump

The increase in the population of Tunisia and the industrial development posed with acuity during the end of the major problems. Without contribution of additional resources, water will then be likely to be done increasingly rare. The solar still is a small production system, yielding on average 2-5 L/day. In this study we propose a solar distiller assisted by a heat pump. The design of this distiller uses for the evaporation of water and its condensation two phenomena are studied Simple Solar Distiller （SSD） and Simple Solar Still Distiller Hybrid with heat Pump （SSDHP）. The performance is less than 2 L/mVday and a performance of 30% for the SSD. But the SSDHP is 12 L/m2/day, the energetic efficiency reaches 90%.

低倍聚光光伏/光热与地源热泵集成系统综合分析及优化

将光伏/光热利用与地源热泵相互耦合,有望利用光伏余热避免热泵性能衰减,还可利用光伏电力部分满足热泵电能需求,前景广阔。构建了低倍聚光光伏/光热与地源热泵的集成系统运行仿真模型,对系统开展了运行性能分析;并进一步研究了系统全生命周期成本的关键影响规律。结果表明:集成系统光伏年均发电效率达17.73%,较单一运行系统提升9.58%,光伏/光热装置的光伏余热可有效减少土壤温度衰减,热泵长时运行性能较参比系统提升16.58%;系统运维成本随光伏/光热装置和地源热泵规模增加而减少,投资成本随之增加,总的全生命周期成本随规模增加先减后增;以全生命周期成本为目标函数,基于粒子群算法开展系统经济性优化,全生命周期成本较最大规模容量设计降低31.52%。相关结论可为光伏/光热与地源热泵集成系统优化设计提供理论参考。

某住宅小区温湿度独立控制空调系统设计

以南京某住宅项目为例,介绍了该项目复合式地源热泵系统、空调水系统、新风系统、空调末端、温湿度及防结露控制。该空调系统采用集中冷热源、分户换热系统,节省了管网投资,降低了输送能耗。用户侧定压补水采用竖向分区减压补水,控制用户侧毛细管系统工作压力,提高了毛细管辐射末端可靠性及使用寿命。置换新风系统采用局部微降板埋地处理,以节省户内空间。其竖向分区的新风系统减小了户内风井面积,增加了使用面积,由双冷源深度热回收新风机组集中回收排风能量,优化了冷凝器配置,热泵回收低温排风能量,提高了内置热泵效率。该项目系统设计对住宅毛细管辐射系统设计具有一定的参考价值。

基于空气源热泵能效提升的物理和数据混合驱动模型研究进展

由于在实际运行中受环境条件和用户行为等多种因素的影响,空气源热泵系统的实际运行能效与理论能效存在较大差异,切实提升其实际运行能效水平是亟待解决的问题。本文首先对基于空气源热泵能效提升的混合驱动模型进行描述,然后从预测和控制以及故障诊断2个方面阐述现有的混合驱动模型,并总结物理信息可融入数据驱动模型的方式,最终提出能效提升应重点关注的混合驱动可解释性建模的研究方向,为进一步提升空气源热泵实际运行能效提供参考。

Heat flow balance and control strategies for a large GSHP

The possibility of underground imbalance between heat emission and absorption has a negative impact on the performance of ground-source heat pump systems （GSHPs）. Numerical and experimental researches were made in a residential building, which is supplied with a GSHP system and a ceiling radiation system combined with a replacement fresh air system. EnergyPlus simulations were used to estimate heating and cooling loads, and to assess the heat generated from the water pump, the fan and the heat pump unit. Then, Fluent simulations were used to compare three different control strategies of handling the underground heat exchange. These simulations were strongly based on an experimentally verified model. It is obtained that a ratio between cooling and heating loads is 5.08 ： 1 in a case study in Nanjing. Moreover, the control strategy based on the starting time is more efficient and reliable than the temperature and temperature difference strategies to control the underground heat exchange.

Numerical simulation on heat transfer performance of vertical U-tube with different borehole fill materials

Heat exchange performance of vertical U-tube heat exchanger was studied with two different borehole fill materials and CFD software. Borehole surface temperature and water temperature distribution were simulated on the condition of continuous operation for 8 h in winter with inlet water temperature being 10℃. The results show that there is no obvious difference on heat exchanger performance between the two different borehole fill materials.

Techno-economic analysis of single U-tube and double U-tube heat exchangers in Chongqing area

On the basis of practical projects in Chongqing,the thermal performance of heat exchangers (single U-tube type and double U-tube type) of the ground-source heat pump (GSHP) system in the hot summer was obtained and analyzed. The data obtained from test could match with the result deduced from theoretical calculation. From the test results,the cooling capacity of double U-tube is 1.6 times that of single U-tube. Taking cost per depth per watt Clq as the evaluation standard,Clq of single U-tube is 4.69 RMB$/W,and Clq of double U-tube is 3.14 RMB$/W. The double U-tube heat exchangers usage should be prioritized.

考虑可再生能源消纳的建筑综合能源系统日前经济调度模型

“双碳”战略目标下,随着以新能源为主体的新型电力系统与分布式智能电网建设的不断推进,具有随机性特点的可再生能源发电大规模并网消纳问题日益凸显。本文面向建筑综合能源系统提出一种日前经济调度模型,旨在利用其多元化负荷需求与灵活性调节的特点,在满足用能需求与电网交互的基础上最大程度实现可再生能源的就地消纳。首先,根据建筑能耗特性,通过配置地源热泵等具有高能效比的电制热设备来解耦热电联产“以热定电”的运行模式、并引入含有蓄电池和储热罐的混合储能装置来进一步增强系统调节能力。然后,考虑供需平衡、设备出力、储能运行、联络线交换功率等约束条件,以含有机组启停、弃风弃光损失等费用在内的总运行成本最小为目标函数,建立日前经济调度模型,并调用CPLEX求解该混合整数线性规划问题。最后,根据设置的不同场景,以系统运行成本、能源利用率和可再生能源消纳能力为评价指标进行算例仿真。仿真结果表明:相较于传统的热电分供模式,设置地源热泵和混合储能系统的综合能源系统可以降低约50%的运行成本,能够提高近50%的能源利用率,且可以完全消纳可再生能源,并随着能量转换装置能效比的提升能够进一步的降低运行成本,具有较好的可操作性与社会经济效益。

Performance Study of a Hybrid Heat Pump Dryer based on Numerical Analysis and Experimental Set-up

Seafood,especially sea cucumbers and oysters are an expensive delicacy in several Asian countries.Traditional sun-drying of these products takes 3 to 4 days and fetches a lower market price.Modern industrial drying machines used for seafood drying are unable to dry sea cucumbers and oysters without texture and color degradation as they are delicate,temperature-sensitive and have longer drying time.An economical drying system that does not cause texture or color degradation is the heat pump drying system and is commonly applied for agriculture and fabric drying.In this study,the heat pump technology is applied to develop two hybrid dryer models(bottom discharge and front discharge)to dry shellfish and sea cucumbers in large scale for storage and transportation.Each model is tested in a laboratory-scale with wet sponges as input material for its dehumidification capacity and the power consumed to attain the target dryness.The front discharge model is found to have rapid drying capability and economy.Computational fluid dynamic tools are used to study the hot air flow behavior and flow uniformity inside the drying chamber.The front discharge model showed smooth uniform flow over the trays with fewer losses in the flow velocity.The front discharge model with higher drying rate,lower power consumption and uniform airflow distribution over the trays is chosen for the industrial-scale design.

大型建筑群复合式热泵供热供冷技术研究及规模化应用

建筑供热供冷是社会各界高度关注的民生工程,热泵是将热能从低品位提升到高品位的高效低碳供能方式,也是国际建筑领域实现碳中和的重要途径。本项目针对大型建筑群复合式热泵供热供冷系统存在总冷热负荷动态预测方法缺失、规划设计体系不完备、系统运行能效低、关键技术和产品不配套、规模化推广难度大等问题,以提升复合式热泵系统能效、有效推进规模化应用为目标,系统性地开展了“负荷预测-优化设计-智慧运行-关键产品-标准推广”的全链条创新工作:提出了基于建筑特征、用户需求的大型建筑群供热供冷系统总负荷动态预测方法,开发了冷热动态负荷特征因子数据库和建筑群负荷集合寻优工具;提出了一种多场景复合式热泵系统能源总线架构理论,建立了仿真平台及综合评价体系,形成了系统容量弹性配置方法;建立了数字孪生复合式热泵系统模型,提出分层控制架构和预测方法,建立了智慧优化运行控制体系;研发了大型复合式热泵系统的关键技术和成套产品;制定了相关工程标准。相关研究成果实现了规模化稳定高效利用可再生能源供热供冷的技术突破,对推进建筑用能方式变革和实现建筑领域国家双碳战略起到重要支撑作用。

基于Transys的太阳能-空气源热泵复合供暖系统优化分析

以西安市周边地区农村住宅为研究对象,基于瞬时系统模拟仿真程序(Trnsys)软件对太阳能-空气源热泵复合供暖系统进行模拟仿真,研究不同集热器倾角和不同蓄热水箱体积对热泵供热量、集热水箱供热量、热泵能耗、系统能耗和性能系数(COP)的影响。结果显示:在最优倾角55°和最优蓄热体积25 m^(3)的条件下,太阳能与空气源热泵复合系统在11月15日至3月15日之间的系统能耗最低,为75394 kWh。其中,空气源能耗为74573 kWh,热泵COP为3.467,系统COP为3.98。研究结果为太阳能-空气源热泵复合供暖系统的设计及优化提供参考。

昆明地区某泵房复合通风设计

昆明地区夏季通风室外计算温度较低,具备较好的自然通风条件,半地下泵房采用自然通风能满足全年绝大多数时间的散热要求。半地下泵房引水泵站连续运行时间长、供水安全性要求高,为满足极端室外空气温度条件下的泵房散热要求,应同时设计机械通风系统。自然通风与机械通风相结合的复合通风系统具有运行管理简单、保证率高、运行能耗低等优点。