天然气在空调供热中的应用分析

天然气是清洁的一次能源.在空调供热中推广应用天然气可减少因空调供热引起的电网峰谷差,符合我国的能源和环境保护政策.本文介绍了几种以天然气为一次能源的空调供热系统,包括燃气溴化锂吸收式热泵、燃气机制冷空调样机及其测试性能和冷热电联供系统(CCHP).     

低温环境下复叠式燃气机热泵的供热性能研究

为了提高燃气机热泵在低环境温度下的制热性能,本文将燃气机热泵技术与复叠式热泵技术相结合,提出了应用于低环境温度下的复叠式燃气机热泵（CGEHP）系统。使用MATLAB软件,建立了CGEHP数学模型。分析了燃气发动机转速、环境温度和系统进水温度对系统供热性能（总供热量、制热性能系数（COP）以及一次能源利用率（PER））的影响规律。结果表明：当环境温度分别为﹣20、﹣15和﹣10 ℃,以NH3-LiNO3作为吸收式热泵系统工质,发动机转速为1 500 r/min时,PER分别为1.0、1.02、1.04,比常规空气源电热泵系统分别提高了24%、15%、5%。     

供热空调系统效率计算方法

为了明确供热空调系统的能质利用情况,基于单耗分析理论和方法对供热空调系统的分析进行了进一步的研究和探讨。讨论了几种典型供热空调系统形式(锅炉供热、电热供热、热泵空调、吸收式冷热水机组)的效率计算方法,并总结出效率通式。为表征系统整个运行期的平均效率,提出了两种使供热空调系统的分析方法更为全面的方法(供热/冷量加权温度法和燃料加权法),并结合示例全面分析了基于热力学第一定律的一次能源利用率和基于热力学第二定律的效率,从而更为全面地了解各系统在全工况下的能源(质)利用情况。     

冷热水联供机组性能实验研究

建立了燃气内燃机驱动的冷热水联供系统,测量了空调名义工况条件下机组的制冷和供热性能,并实验研究了内燃机的转速对机组制冷和供热的影响特性。实验结果表明系统在空调名义工况条件下的制冷量467．1kW,供热量为148．7kW,一次能源利用率达1．9,与常规电制冷＋锅炉供热相比能源节约率达37．8％。在实验测试的内燃机转速范围内制冷系统的制冷量和余热回收供热量随内燃机转速的降低而降低,但制冷系统和冷热水联供系统能源利用率均随内燃机转速的降低而升高,表明机组在部分负荷运行时,应优先调节内燃机的转速,从而确保系统具有较高的能源利用率。该联供系统有效回收利用了内燃机的余热,提高了能源利用率,商业化前景较好。     

户式中央空调的一次能耗比较

对比了不同户式中央空调在名义工况、变工况和部分负荷工况下的一次能源利用率, 结果表明:当电能由煤转化时,在名义工况和变工况条件下,户式燃气空调的一次能源利用率稍高;当电能由天然气转化而来时,电制冷户式空调的一次能源利用率比户式燃气空调的高;多联空调机组在部分负荷工况下的一次能源利用率最高,其能源利用效率最为显著。     

燃气机驱动CO2跨临界循环热泵系统

以天然气为能源，以CO2为工质的燃气机驱动CO2跨临界循环热泵系统可以最大限度地降低总有效温室效应指数，提高一次能源利用率，减小对环境的污染，而且其运行费用也低于普通电动热泵，具有很好的发展前景。     

燃气发动机与电动机联合驱动热泵供热工况运行策略研究

由燃气发动机和电动机联合驱动的混合动力热泵(HPHP)是提高燃气供热和制冷效率的发展方向之一,但其在系统设计和运行策略上还存在提升空间。本文提出了供热和供冷均由燃气发动机与电动机联合驱动的HPHP,并建立数学模型。通过模型计算,针对设计工况下发动机占最大输出功60%下的HPHP,并与燃气机热泵(GEHP)和电热泵(EHP)进行对比,分析了不同环境温度下的发动机效率和一次能源利用效率(PER)。结果表明:HPHP可减小发动机容量,当环境温度为-9～-1℃时,HPHP的发动机效率相比于GEHP提高了3.2%～9.4%;对于PER,HPHP与EHP相比于GEHP有较大的提高;当室外温度为-9～3℃时,与EHP相比,HPHP的PER比EHP提高了1.2%～9.5%,当温度继续升高时HPHP与EHP的PER较接近。因此从整个供暖季的能效角度考虑,HPHP系统相比于GEHP和EHP具有较大的节能潜力。     

五种供热空调系统的技术经济分析及建议

对５种供热空调系统的一次能源利用率、年单位面积运行能耗费用、年单位面积供空调总成本等进行分析比较。对比较结果进行分析提出应该按照系统消耗能源需要的治理技术和工艺情况（包括生产该能源时的排放治理情况）收取系统能源消耗排放治理费,并就该项费用指标对装置的节能环保性能及经济性的影响进行了分析研究。     

燃气机驱动C02跨临界循环热泵系统

以天然气为能源,以CO2为工质的燃气机驱动CO2跨临界循环热泵系统可以最大限度地降低总有效温室效应指数,提高一次能源利用率,减小对环境的污染,而且其运行费用也低于普通电动热泵,具有很好的发展前景.     

迎接"西气东输",积极开展燃气空调的研制

中国空调使用量居世界前列，且消耗能源大部分为电力，对电网安全运行造成极大危害，另一方面，随着“西气东输”工程的实施，燃气已在城市的普及使用，但燃气用量不平衡，发展燃气空调可以缓解电力紧张状况，又可调节燃气用量季节的不均性，并且有利于节约能源，保护环境，文中还介绍了燃气空调的主要形式，指出了燃气发动机驱动热泵和小区热、电、冷三联供是发展方向。     

Thermal modeling of gas engine driven air to water heat pump systems in heating mode using genetic algorithm and Artificial Neural Network methods

The gas-engine driven air-to-water heat pump, type air conditioning system, is composed of two major thermodynamic cycles (including the vapor compression refrigeration cycle and the internal combustion gas engine cycle) as well as a refrigerant-water plate heat exchanger. The thermal modeling of gas engine driven air-to-water heat pump system with engine heat recovery heat exchangers was performed here for the heating mode of operation (in which it was required to model engine heat recovery heat exchanger). The modeling was performed using typical thermodynamic characteristics of system components, Artificial Neural Network and the multi-objective genetic algorithm optimization method. The comparison of modeling results with experimental ones showed average differences of 5.08%, 5.93%, 5.21%, 2.88% and 6.2% which shows acceptable agreement for operating pressure, gas engine fuel consumption, outlet water temperature, engine rotational speed, and system primary energy ratio.     

夏季冷热联供模式下的燃气机热泵机组性能分析

本文建立了一套以R134a为制冷剂工质、以天然气为一次能源驱动开启式压缩机做功的燃气机热泵系统,研究了当蒸发器进水温度为12～22℃,室外环境温度为24.2～35.6℃,发动机转速为1 400～2 000 r/min,夏季冷热联供模式时,空气源燃气机热泵(GEHP)机组的性能。结果表明:发动机转速和蒸发器进水温度的变化对系统性能的影响大于室外环境温度变化的影响。随着发动机转速由1 400 r/min增至2 000 r/min,系统COP_1、COP_2、PER_1、PER_2分别减小了15.5%、9.9%、18.8%、13.5%。在工况范围内,机组冷水出水温度可达6.7～19.3℃,热水出水温度可达40.7～61.7℃,考虑余热回收情况下系统PER_2可达1.14～1.45。     

Simulation and validation of a hybrid-power gas engine heat pump

Hybrid-power gas engine heat pump (HPGHP) combines hybrid power technology with gas engine heat pump, which can keep the gas engine working in the economical zone. In this paper, a steady-state model of the HPGHP in heating condition has been established, the optimal torque curve control strategy is proposed to distribute power between the gas engine and battery pack. The main operating parameters of the HPGHP system are simulated on Matlab/Simulink and validated by experimental data, such as operating temperature, coefficient of performance (COP), fuel-consumed rate, etc. Heating capacity and COP of the heating pump system are validated under different ambient temperatures and water flow rates. The simulation and experiment results shows acceptable agreement, the maximum difference is respectively 8.9%, 5.9%, 9.5% and 8.2% for engine torque, motor torque, reclaimed heat and fuel-consumed rate. Based on the simulation results, HPGHP has the lowest fuel-consumed rate of 283 g (kWh)⁻¹ at engine speed of 3000 rpm; the PER of HPGHP system is about 15.9% and 11.4% higher than the GHP under the same load in Mode C and D.     

Supply of cooling and heating with solar assisted absorption heat pumps: an energetic approach

The primary energy consumption of two kinds of solar assisted absorption systems (solar assisted absorption chiller during summertime and heat pump during wintertime or solar assisted absorption chiller with direct gas combustion for heating during wintertime) is compared with the primary energy consumption of a compression chiller which can work as a heat pump during wintertime. For the absorption systems three technical options were considered: a single effect machine; a double effect machine with the solar energy delivered to the lower temperature desorber and combustion heat of a gas burner delivered to the higher temperature desorber; a double effect machine with both solar energy and combustion heat delivered to the higher temperature desorber. The analysis performed in this article shows that solar assisted absorption chillers, absorption heat pumps and direct solar heating systems even with low and intermediate solar fractions can operate with considerably less primary energy consumption than compression systems. Further, the necessary solar collector area to achieve that goal is compatible with roof area available in buildings. It was also verified that, for the double effect absorption machines, there is no advantage in delivering the solar energy to the higher temperature desorber, thus establishing as preferable the solution in which it is delivered to the lower temperature desorber.     

Experimental study on performance of a biogas engine driven air source heat pump system powered by renewable landfill gas

The equipment configuration of a landfill gas (LFG) fueled biogas engine driven air source heat pump system was studied. The process flow for collecting and purifying LFG was analyzed, and the LFG collection and purification method was determined. An experimental apparatus was set up, and the effect of biogas engine speed variation on LFG consumption, exhaust fume temperature of biogas engine, recovered waste heat from exhaust fume and cylinder liner, coefficient of performance (COP) of the heat pump and primary energy ratio (PER) of the system were experimentally tested. The results indicated that LFG consumption and biogas engine exhaust fume temperature increased with biogas engine speed. When the biogas engine operated in the 70%–90% rated speed range, the system heat output and exhaust fume waste heat recovery rate would be relatively higher. In addition, the maximum COP and PER reached 4.2 and 1.4 respectively.     

沼气机压缩式热泵系统的构建与经济性分析

由沼气发动机驱动的热泵（BHP）除能够保证一般热泵功能外,还能够充分回收利用沼气发动机的余热。根据对BHP的系统构建及一次能源利用率（PER）的计算结果,分析BHP系统的经济性及其对环境保护的作用。结果表明：BHP系统在经济性及环保方面都具有明显的经济价值和现实意义。     

Study of using a capillary tube in a heat pump dishwasher with transient heating

For competitive purposes, manufacturers of household appliances need to produce appliances that use less electricity. One way of doing this for a dishwasher is to add a heat pump system. Previous studies using R134a as refrigerant have shown that the addition of a heat pump can reduce total electricity consumption by about 24%. This paper reports on the use of a capillary tube in a heat pump dishwasher during the transient heating period. Working with an available compressor, the mass of R600a and the length of a 0.9 mm capillary tube were varied in order to find the configuration with the lowest electricity consumption. Three methods of calculating the length of the capillary tube were used to determine five lengths for evaluation. The results show that using a single capillary tube throughout the transient heating period yields similar electricity consumption to a variable expansion device which occurred by switching the capillary tube between two or three different lengths during the heating period.     

外绕微通道冷凝器空气源热泵热水器仿真与优化

空气源热泵热水器比燃气或电热水器更为节能。本文提出了一种外绕微通道冷凝器,可以减少制冷剂充灌量、提高换热效率、降低成本、提高安全性。建立了热泵热水器的准稳态系统模型,制冷剂侧采用稳态模型,水箱和水侧采用动态模型。通过实验证明了该系统模型可以准确地预测时变的系统功耗、水温,以及系统时均COP。通过仿真分析,发现水箱隔热层可以缩短水的加热时间、并提高系统COP约9.2%。增大冷凝器也可提升系统COP,但几乎不改变水的加热时间。最后提出了微通道冷凝器的三流程优化设计方法。     

Conception of combination of gas-engine-driven heat pump and water-loop heat pump system

Conception of combination of gas-engine-driven heat pump (GHP) and water-loop heat pump system (WLHPS) is firstly presented in the paper in order to reduce the energy consumption of air conditioning system further. Design of the new system is introduced through an actual project in China and compared with a conventional air-conditioning system (CACS) and conventional WLHPS (EHP-WLHPS) in terms of technical characteristics and payback period. It is found that the payback period of GHP-WLHPS is about 2 years when compared with CACS and 2.6 years with EHP-WLHPS on the average. So it is worth being more widely applied. And several barrier to application are also discussed.     

A novel parallel-type hybrid-power gas engine-driven heat pump system

This paper presents a novel concept to integrate a heat pump system and a power system which form a hybrid-power gas engine-driven heat pump (HPGHP) system. The power system of the HPGHP system includes an engine, a motor, a set of battery packs, a continuous variable transmission device and a power-control module. The engine in the power system is capable of operating constantly with high thermal efficiency and low emissions during the four different operating modes: for operating mode A, the ICE powers directly to match the compressor's demand load by throttling the natural-gas flow or adjusting the speed of the ICE, correspondingly the battery packs are disengaged and the ICE operates alone; for operating mode B, the ICE operates in the unique condition with the lowest fuel consumption ratio, meanwhile, the battery packs discharge to provide the supplementary power by the power-control module; for operating mode C, the ICE operates in the unique condition with the lowest fuel consumption ratio, and the redundant power provided by the ICE is converted by the motor to charge the battery packs, here, the motor is used as a generator; for operating mode D, the ICE is disengaged and the battery pack is used alone. Simulation results of the power system showed that for a conventional gas engine-driven heat pump (GHP) system the maximum and minimum thermal efficiencies of the power system are 33% and 22%, respectively; compared with the conventional GHP system, the power system in the novel HPGHP system has superior performance with the maximum and minimum thermal efficiencies of 37% and 27%, respectively.