A new concept in gas-fired heat pump reversed rectification heat pump

The reversed rectification heat pump (RRHP) is a novel type of absorption heat pump developed at Laboratoire des sciences du génie chimique (LSGC) in the research group of Professor Le Goff. The distinctive characteristic of the RRHP is that both the separator and the absorber are multi-stage gas contacting units of a type commonly used in the process industry and each composed of the multi-stage contactor, an evaporator and a condenser. The separator is a conventional rectification unit in which the working fluid is separated into a rich and a lean phase which are recombined in the absorber. The absorption is an exact reversal of the rectification, both units having inverted flow diagrams; for this reason the absorption is refered to as reversed rectification. This heat pump can produce simultanious heat and cold and provides significant primary energy savings and reduction of harmful environmental effects.     

A transcritical CO2 heat pump for simultaneous water cooling and heating: Test results and model validation

Working prototype of a transcritical CO₂ heat pump system for simultaneous cooling and heating of water is designed and developed based on numerical simulation studies. System behaviour and performance of the system have been studied experimentally for various operating parameters such as system pressure, water mass flow rate, water inlet temperature and expansion valve opening. Finally, the system simulation model predictions have been validated by the test data. Test results show the effect of water mass flow rate to be modest for both evaporator and gas cooler, whereas the effect of water temperature at the inlet to the gas cooler on system performance is significant. The expansion valve opening has a significant effect as well near the full valve closing condition (up to 20°). Validation of the simulation model shows reasonably good agreement (a maximum deviation of 15%) with the test data exhibiting fairly similar trends. Copyright © 2008 John Wiley & Sons, Ltd.     

太阳能辅助热泵干燥粮食的数值模拟研究

粮食的干燥过程实质上是多孔介质热湿耦合传递的过程。基于多孔介质热质传递理论,通过数值模拟的方法,针对利用太阳能辅助热泵干燥粮食时热风随时间变化的情况,采用综合温度和空气绝对湿度作为瞬态边界条件来对干燥过程中粮食内部温度和水分的变化进行模拟研究。模拟结果显示小麦水分在干燥150h后达到安全水分13.6%(干基),而实验结果显示小麦水分在干燥135h后达到安全水分13.6%(干基),二者对比相差不大,并且模拟温度与试验温度吻合较好。     

Performance assessment of a horizontal-coil geothermal heat pump

This paper evaluates the performance of a geothermal heat pump in Iran. An air-to-air 5.275 kW heat pump has been changed and redesigned to a geothermal heat pump system for the first time in Iran. Air-to-air condenser has been replaced by a tube-in-tube heat exchanger and assembled system has been tested under ARI-325 standard at the national energy lab of Iran and the results have been compared with the original system. Then, local weather conditions and soil properties of Tabriz (located at the north-west of Iran) have been applied and geothermal coil has been designed. Coil has been connected to the heat pump and the average coefficient of performance (COP) of rather more than three has been recorded in cooling mode. Results obtained from experimental measurements show that horizontal GSHP systems can be used for Tabriz-like climates in Iran. Copyright © 2006 John Wiley & Sons, Ltd.     

A spectral model for transient heat flow in a double U-tube geothermal heat pump system

This paper introduces a semi-analytical model based on the spectral analysis method for the simulation of transient conductive-convective heat flow in an axisymmetric shallow geothermal system consisting of a double U-tube borehole heat exchanger embedded in a soil mass. The proposed model combines the exactness of the analytical methods with an important extent of generality in describing the geometry and boundary conditions of the numerical methods. It calculates the temperature distribution in all involved borehole heat exchanger components and the surrounding soil mass using the fast Fourier transform, for the time domain; and the complex Fourier and Fourier-Bessel series, for the spatial domain. Numerical examples illustrating the model capability to reconstruct thermal response test data together with parametric analysis are given. The CPU time for calculating temperature distributions in all involved components, pipe-in, pipe-out, grout, and soil, using 16,384 FFT samples, for the time domain, and 100 Fourier-Bessel series samples, for the spatial domain, was in the order of 3 s in a normal PC. The model can be utilized for forward calculations of heat flow in a double U-tube geothermal heat pump system, and can be included in inverse calculations for parameter identification of shallow geothermal systems.     

地源热泵垂直埋管的传热模型及计算

建立了垂直埋管地源热泵地热换热器的传热模型,采用有限差分法建立了垂直U型埋管换热器瞬态传热模型的解析解;并且在不同的工况下进行实验测试,与模拟结果进行了对比,结果表明模拟与实验能较好地吻合,从而使模型的正确性得到了验证。可为地源热泵的设计和运行提供理论指导。     

Seasonal cooling performance of a ground-coupled heat pump system in a hot and arid climate

The goal of the present study is to validate the cooling performance of a ground-coupled heat pump system established in Fırat University, Elazığ (38.41°N, 39.14°E), Turkey. The cooling load of the test room was 3.1 kW at design conditions. The experimental results were obtained from June to September in cooling season of 2003. The ground heat exchanger was used, and it was buried with in 2 m depth trench. The average cooling performance coefficient of the system (COP_overall) was obtained to be 2.01. The results obtained from experimental measurement showed that these systems could be used safely, reliably and efficiently at the lowest possible cost for Elazığ, Turkey climatic conditions. Especially, the seasonal energy efficiency ratio (SEER) of this system is moderate at longer-term testing.     

Feasibility study on novel hybrid ground coupled heat pump system with nocturnal cooling radiator for cooling load dominated buildings

When the ground coupled heat pump (GCHP) system is utilized for air conditioning in cooling load dominated buildings, the heat rejected into ground will accumulate around the ground heat exchangers (GHE) and results in system performance degradation. A novel hybrid ground coupled heat pump (HGCHP) system with nocturnal cooling radiator (NCR) works as supplemental heat rejecter is proposed in this paper to resolve this problem. The practical analytical model of NCR and novel HGCHP system are established. The computer program based on established model is developed to simulate the system operation performance. The novel HGCHP system is designed and simulated for a sample building located in Hong Kong, and a simple life cycle cost comparisons are carried out between this system and conventional GCHP system. The results indicate that it is feasible to use NCR serves as supplemental heat rejecter of the novel HGCHP system for cooling load dominated buildings even those located in humid subtropical climate areas. This novel HGCHP system provides a new valuable choice for air conditioning in cooling load dominated buildings, and it is especially suitable for buildings with limited surface land areas.     

Analysis of the performance of a multi-bed adsorption heat pump using a solid-side resistance model

An analysis of the coefficient of performance and specific cooling power for a four-bed adsorption heat pump, using a solid-side resistance model, is presented. Methanol and an activated carbon are the adsorption pair. An Arrhenius form of solid-side mass diffusivity was adopted. A plate-fin type insert was considered as the heating/cooling element in adsorbers. The result shows that, for large grain-size activated carbon, the intra-particle mass diffusion resistance significantly affects the adsorption and regeneration rates. Both the coefficient of performance and the specific cooling power increase with the overall heat transfer coefficient, regeneration and evaporation temperatures, but decrease with an increase of the condensing temperature and time constant of the insert. The coefficient of performance considerably increases with a decrease of the insert heat capacitance. An optimum cycle time, corresponding to a maximum specific cooling power, was found. To achieve a high specific cooling power for short cycle time operations, small grain-size activated carbon should be selected as the adsorbent. In addition, a small time constant of the insert and a large overall heat transfer coefficient are also highly recommended.     

土壤源热泵地下垂直换热埋管周围非稳态温度场的数值模拟

针对土壤源热泵地下垂直U型换热埋管,建立了周围土壤的非稳态温度场的数学模型,并利用隐式有限差分法进行了数值模拟。通过对制冷和制热工况的模拟,得到土壤温度沿径向的变化规律、埋管出水温度的变化规律及埋管的热作用半径的变化规律。     

An empirical model for a heat pump dehumidifier drier

Data obtained from laboratory measurements on a dehumidifier using R134a in a scroll compressor are analysed to establish empirical sub-models for the principal drier components. A model for the dehumidifier system is set up by coupling the sub-models using energy and mass balances. The performance data obtained using the system mdoel is in good agreement with the measured data obtained with four system configurations under a wide range of operating conditions. The model is used to demonstrate how the performance for the dehumidifier relates to that for the coupled kiln-dehumidifier system. By resizing the heat exchangers it is shown that the energy efficiency of the prototype system can be increased significantly, the dehumidifier specific moisture extraction rate approaching 10 kgkWh⁻¹ at high humidity.     

An Experimental Study on the Performance of a Stainless Steel-Water Loop Heat Pipe under Natural Cooling Condition简

Aiming to improve the thermal characteristics of modern electronics, we experimentally study the performance of a stainless steel/water loop heat pipe （LHP） under natural cooling condition. The LHP heat transfer performance, including start-up performance, temperature oscillation and total thermal resistance at different heat loads and with different incline angles have been investigated systematically. Experimental results show that at an optimal heat load （i.e. 60 W） and with the LHP being inclined 60~ to the horizontal plane, the total thermal resistance is lowered to be -0.24 K/W, and the temperature of evaporator could be controlled steadily at around 90~C.     

Chemical heat pump using heat of reversible catalytic reactions

One of the most important objects of research in the field of energy conservation is development of a high temperature heat pump for the industrial sector. In this framework this paper introduces a new concept of heat pump, which is a hybrid between a compressor and chemical heat pump, where instead of the latent heat of liquids, the proposed system uses the heat of gaseous catalytic reversible reactions (type A → B + C). This paper proposes a simple scheme with a mathematical model for the calculation of the parameters necessary to qualify the behaviour of the Heat Reaction Chemical Heat Pump (HRCHP). The Coefficient of Performance (COP) is calculated as a function of the temperature of the heat source, the temperature to which the pump upgrades the heat and the conversion of the chemical reaction. A more optimized scheme is prospected.     

Application of a heat pump system using untreated urban sewage as a heat source

Untreated urban sewage contains large amounts of thermal energy; and its temperature is suitable as a heat source in heat pumps for the heating and cooling of buildings. However, it is not widely used in heat pump systems due to the problem of filth. This paper presents an untreated sewage source heat pump (USSHP) system in which auto-avoiding-clogging equipment is used to continuously capture suspended solids in the sewage. Thus, the block problems caused by filtration and fouling in the heat exchanger tubes can be efficiently resolved in this system. In an actual engineering application, the characteristic parameters of USSHP system are tested under typical operating conditions for heating status. Based on the test results, the performances of the USSHP system are examined. The results indicate that the thermal resistance of the convective heat transfer and fouling on the sewage side in the sewage exchanger is 80% of its total thermal resistance. The COP of the heat pump unit and the COP of the USSHP system are 4.3 and 3.6, respectively.     

燃气热泵与电动热泵的技术经济比较

结合现有产品的技术水平,分析比较了燃气热泵与电动热泵的一次能源利用率.针对不同电价、不同燃气价的情况计算了两种热泵的运行成本.由计算结果绘制的图表为空调方案的选择提供了有益的参考.     

水源CO2热泵的全工况性能与匹配性分析

通过对60kW水源CO_2热泵的实验测试,在获得的911组实验数据的基础上,建立了用于反映热泵系统性能和循环参数随运行工况变化趋势的BP神经网络拟合模型,综合分析了系统在供水温度为55~100℃、回水温度为10~50℃、热源温度为5~50℃和电子膨胀阀开度为50~400步的全工况范围内的性能,从而为该类型热泵系统性能的预测和系统设计提供了数据参考。在对四种工况下,即15/55/15℃、15/90/15℃、15/90/30℃和30/90/30℃时系统运行参数的比较分析的基础上,定性评价了系统在全工况范围内的匹配性。     

Analysis of a heat pump with solid desiccant tube bank

In this paper, the analysis of silica gel formed in a staggered tube bank arrangement for the reduction of energy consumption in a heat pump dehumidifier is presented. The mathematical models for the desiccant and the heat pump have been developed. The simulated results agree quite well with those of the experiments. The desiccant could reduce the heat pump load by about 7–20 per cent at the inlet air conditions of about 30–50°C and 70–90 per cent RH. Copyright © 2002 John Wiley & Sons, Ltd.     

小型风冷热泵机组工况特性实验研究

以R22为工质,通过对风冷热泵冷热水机组变工况特性实验测试,全面分析测试机组工况特性。提出了机组性能改进措施及方法,实现风冷热泵节能优化,同时给出机组制冷量工况函数和COP工况函数及相应性能曲线,这对机组的设计、匹配和选型有重要的指导意义。     

Experimental investigation of thermal performance of a solar assisted heat pump system with an energy storage

An experimental solar assisted heat pump space heating system with a daily energy storage tank is designed and constructed, and its thermal performance is investigated. The heating system basically consists of flat plate solar collectors, a heat pump, a cylindrical storage tank, measuring units, and a heating room located in Gaziantep, Turkey (37.1°N). All measurements are automatically collected as a function of time by means of a measurement chain feeding to a data logger in combination with a PC. Hourly and daily variations of solar radiation, collector performance, coefficient of performance of the heat pump (COP_HP), and that of the overall system (COP_S) are calculated to evaluate the system performance. The effects of climatic conditions and certain operating parameters on the system performance parameters are investigated. COP_HP is about 2.5 for a lower storage temperature at the end of a cloudy day and it is about 3.5 for a higher storage temperature at the end of a sunny day, and it fluctuates between these values in other times. Also, COP_S turns out to be about 15–20% lower than COP_HP. Copyright © 2004 John Wiley & Sons, Ltd.