共查询到17条相似文献,搜索用时 640 毫秒
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为了分析火积耗散在气冷器内分布情况及影响,利用CFD数值模拟技术建立直管套管式气冷器模型,对超临界CO2套管式气冷器内CO2与冷却水之间的热量传递过程进行数值模拟研究。通过改变操作压力、温度、质量流量等参数进行计算,分析火积耗散沿管长分布情况,研究温度、质量流量、压力的变化对套管式气冷器火积耗散的影响。结果表明:随着CO2进口温度升高,火积耗散增大,但冷却水温度的改变对火积耗散影响小,可忽略不计;随着冷却水质量流量的增大,火积耗散减小,火积耗散在CO2入口相对于在套管气冷器其他位置处,数值最大。相较于冷却水质量流量0.03 kg/s,冷却水质量流量为0.04 kg/s时,火积耗散减小了2.6%,冷却水质量流量为0.05 kg/s时,火积耗散减小了3.2%;随着CO2质量流量增大,火积耗散增大;且随着压力的增大,火积耗散减小。研究结果可以为改进CO2气冷器的结构和提高换热性能提供新的思路和参考依据。 相似文献
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为了提升跨临界CO2热泵系统的性能,利用喷射器替代节流阀植入系统中,在保证喷射器效率的前提下,对系统中各参数之间的相互影响进行了分析,通过建立SEC系统的热力学模型,分析了气冷器CO2出口温度、排气压力、蒸发温度等参数对系统制热系数COPh的影响。结果表明:气冷器CO2出口温度是决定常规系统引入喷射器是否有益的关键,随着排气压力(7~10 MPa)变化,气冷器CO2出口温度(30~55℃)存在一转换温度,只有当出口温度小于转换温度时才有助于提升COPh。同时为了保证系统的安全与运转正常,气冷器CO2出口温度在低于安全值(57℃)的前提下,还应不超过其转换温度。本文进一步研究了增加回热器对提升SEC的热力性能的效果,结果表明,在气冷器CO2出口温度大于31℃时在SEC系统中加入回热器可以有效提升热泵系统的制热性能。 相似文献
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由于CO_2具有环保和独特的热力学优势,其用于家用热泵热水器领域已获得巨大的发展。为研究CO_2热泵热水器系统运行特性受外界因素影响的变化规律,自行搭建了一台空气源CO_2热泵热水器试验台开展试验研究。试验表明随着冷却水体积流量从48.94 L/h增加到75.2 L/h,空气源CO_2热泵热水器系统制热量提升49%,制热系数比原来增加了0.7倍;随着室外环境温度从-3℃升高到13℃,空气源CO_2热泵热水器系统制热量提升28%,制热系数比原来增加了1.5倍,室外环境温度对压缩机的吸气压力影响较大。本文的试验研究结果为后续的CO_2空气源热泵热水器的系统优化提供技术支持。 相似文献
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主要对带节流阀的CO2跨临界水-水热泵系统建立了数学模型,对系统的制热性能进行了模拟计算,并与试验数据做了对比。主要分析了高压侧压力、冷却水和冷冻水的进口温度和流量分别对系统制热系数和制热量的影响。结果表明,模拟计算结果与试验测试值的一致性较好,从而验证了模型的可信度。模拟所得对应最大制热系数的最佳高压侧压力与实验结果存在一定的偏差。系统的制热性能系数和制热量随着冷却水进口温度的升高而降低,随冷冻水进口温度的升高而增大;而且都随着冷却水和冷冻水流量的增加呈现出升高趋势。 相似文献
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运用EES编程建立了水冷热泵系统的数学模型,对系统的制热性能进行了模拟计算,主要分析了室内环境温度、冷却水进口温度和流量对系统制热量性能系数和能效比的影响。模拟结果表明:室内环境温度对系统性能系数和能效比影响很大,随着温度的升高制热系数降低;在一定范围内随着进水温度和流量的升高,系统性能系数和能效比急剧增大,但随后趋于平缓,存在最佳流量。通过模拟研究了运行参数对性能的影响,为实际的开发设计和验证提供了依据。根据理论设计,搭建试验样机,利用空调焓差室对该机组进行试验研究,对试验样机在名义工况下的制冷、制热性能进行了测试,水侧和制冷剂侧热平衡偏差在5%以内,进一步验证了测试的准确性。测试结果表明,制冷工况时的性能系数和能效比均低于制热时的,采用双并联冷凝器设计,对于较大制冷量和制热量热泵系统具有明显优势。 相似文献
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介绍了一种新型商用跨临界CO2热泵空气干燥系统.首先建立了热泵干燥系统所需的翅片式气冷器的物理和数学模型,对气冷器的换热面积进行了计算,同时根据超临界状态下CO2放热特性对气冷器的结构进行设计.在此基础上,建立了跨临界CO2热泵空气干燥系统,并对该系统进行了性能试验研究.试验结果表明,该系统可将常温空气“一次性”加热到100℃,此种工况下空气流量为2.26 m3/h,系统性能系数COP为3.80. 相似文献
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太阳能热泵热水器加热性能的试验研究 总被引:2,自引:0,他引:2
在自行设计制作的试验台上进行了太阳能热泵热水器加热性能试验.定流量循环加热热水时,太阳能热泵热水器比普通太阳能热水器加热速度快3.4倍,集热器效率提高了1倍多.太阳能热泵直流式加热热水时,热水出口温度随热水流量的增加而降低,系统能效比随热水流量的增加而增加;热泵蒸发温度与热水入口温度越高,产生适宜出口温度的热水流量调节范围越大,出口温度相同时则系统能效比越高;太阳能热泵具有即时供热水功能.太阳能热泵热水器采用循环式加热比直流式加热耗时更短,经济性更好. 相似文献
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The operation performance measurement of the air source heat pumps in the field, in which conditions are complicated and the accuracy could not be ensured, is very crucial for its performance evaluation and improvement. In this investigation, a novel method for measuring the heating capacity of the air source heat pump is established. An auxiliary electric heater is installed along the pipeline between the compressor and the condenser, and the refrigerant temperature difference caused by the heater is gathered to calculate the refrigerant mass flow rate based on the energy conservation. The heating capacity is calculated with the measured data of the refrigerant enthalpy at the inlet and outlet of the condenser and the refrigerant mass flow rate of the compressor discharge pipe. The validation results in laboratory tests show that the measured heating capacity accuracy is within 9.2%. It is also found that the impact of the novel test method on the heating capacity of the air source heat pumps is below 1.7%, and the power consumption of the tested units is increasing of within 1.8% compared with it when the electric heater is off. The refrigerant enthalpy difference method with an electric heater presented in this research can be applied to measure the heating capacity of different air source heat pump air heaters accurately in the field, which will be much helpful to improve the performance for cleaning heating in northern China. 相似文献
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Direct contact air conditioning systems, in which heat and mass are transferred directly between air and water droplets, have
many advantages over conventional indirect contact systems. The purpose of this research is to investigate the cooling and
heating performances of direct contact air conditioning system for various inlet parameters such as air velocity, air temperature,
water flow rate and water temperature. The experimental apparatus comprises a wind tunnel, water spray system, scrubber, demister,
heater, refrigerator, flow and temperature controller, and data acquisition system. The inlet and outlet conditions of air
and water are measured when the air contacts directly with water droplets as a counter flow in the spray section of the wind
tunnel, and the heat and mass transfer rates between air and water are calculated. The droplet size of the water sprays is
also measured using a Malvern Particle Analyzer. In the cooling conditions, the outlet air temperature and humidity ratio
decrease as the water flow rate increases and as the water temperature, air velocity and temperature decrease. On the contrary,
the outlet air temperature and humidity ratio increase in the heating conditions as the water flow rate and temperature increase
and as the air velocity decreases. 相似文献
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