R134a在螺旋套管冷凝器中的换热性能实验研究

发布时间：2018-09-18 07:22

【摘要】：对空气源热泵热水器的换热性能进行相关研究尤为重要。这是因为空气源热泵热水器不仅安全,能够达到节约能源的目的,而且安装使用方便、对环境无污染,更重要的是它还具有使用范围广,使用寿命长以及维护费用低等优点。通常来说,制冷工质的特性和冷凝器换热效果的好坏在某种程度上决定了空气源热泵热水器的换热性能的好坏。螺旋套管换热器具有结构紧凑、制造简单、价格便宜以及传热强度高等优点,充分研究螺旋套管换热器的凝结换热过程具有重要的意义。尤其是在制冷剂替代过程中,螺旋套管环形空间制冷剂的换热系数准确性更是研究新型替代制冷剂凝结换热性能所必需的关键参数之一。在当今社会,由于世界环保意识的提高,人们对制冷剂是否环保极为重视。就目前而言,R134a是最理想的替代R22的制冷剂。即使如此,两者的热物性并不相同,因此,对R134a的换热性能及压降特性进行研究对改进原有系统设备,研究、开发新的系统设备具有极为重要的意义。本文以R134a为工质,对空气源热泵热水器采用螺旋套管冷凝器时的换热性能与系统的运行性能进行实验研究。测试了循环加热情况下,螺旋套管冷凝器的总换热量、总换热系数、压缩机吸、排气压力,系统输入功率,制热量,制热系数等随冷凝器循环水流量及冷凝器入口水温的变化情况;同时,还测试了直流稳态情况下,当冷凝器入口水温一定时,螺旋套管冷凝器的总换热量、总换热系数、压缩机吸、排气压力、系统输入功率等随冷凝器进水流量的变化情况。(1)水流循环加热时,冷凝器进水流量一定,随着入口水温的升高,冷凝器总换热量减小,而总换热系数增大,压缩机吸、排气压力和输入功率也是增大的,热泵系统的制热量和制热系数却随入口水温的增大而减小。当螺旋套管冷凝器的进水流量为1.19m3/h,冷凝器的入口水温由25.2℃升高至63℃时,冷凝器的总换热量由7041.79W减小至2847.39W,总换热系数由1184.12W/(m2·K)增大至1643.21 W/(m2·K),吸气压力由0.34MPa升高至0.38MPa,排气压力由0.77MPa升高至2.00MPa,系统输入功率由1040W升高至2100W,系统的制热性能系数COP由4.4减小到1.2,制热量则由1387.83W减小为667.14W。(2)水流循环加热,冷凝器入口水温一定时,随着进水流量的增大,冷凝器总换热量和总换热系数均增大,压缩机吸、排气压力和系统输入功率则是减小的,热泵系统的制热量和制热系数随进水流量的增大而增大。当入口水温保持在24℃,螺旋套管冷凝器的进水流量由1.19m3/h增大至2.16m3/h时,冷凝器的总换热量由4025.72W增大到7565.71W,总换热系数由1472.03 W/(m2·K)增大到3956.29 W/(m2·K),吸气压力由0.36MPa下降至0.35MPa,排气压力由1.38MPa下降至1.27MPa,系统输入功率由1488.67W减小到1423.75W,系统的制热性能系数COP由2.5升高至3.0,制热量则由986.90W增大到1087.06W。(3)直流稳态条件下,当冷凝器入口水温一定时,随着进水流量的增大,螺旋套管冷凝器总换热量和总换热系数是增大的,压缩机吸、排气压力和系统输入功率随冷凝器进水流量的增大反而降低。当入口水温保持在22℃,螺旋套管冷凝器的进水流量由0.26 m3/h增大至0.71 m3/h时,螺旋套管冷凝器的总换热量由3614.24W增大至4165.96W,总换热系数由1999.03 W/(m2·K)增大至2835.92W/(m2·K),压缩机吸气压力由0.32MPa下降至0.30MPa,排气压力由0.84MPa下降至0.62MPa,系统输入功率由1040W减小到920W。本文通过对螺旋套管冷凝器的换热性能及热泵运行性能进行实验研究及理论分析,得到螺旋套管冷凝器换热性能及热泵运行性能与冷凝器入口水温及进水流量的变化关系,该研究有望为制冷剂替代中换热器的优化设计与热泵热水器的节能运行提供参考。
[Abstract]:It is very important to study the heat transfer performance of the air source heat pump water heater. This is because the air source heat pump water heater is not only safe and energy-saving, but also easy to install and use, no pollution to the environment. More importantly, it has the advantages of wide range of use, long service life and low maintenance costs. The characteristics of refrigerant and the heat transfer effect of condenser determine the heat transfer performance of air source heat pump water heater to a certain extent. Spiral tube heat exchanger has the advantages of compact structure, simple manufacture, low price and high heat transfer intensity. Especially in the process of refrigerant substitution, the accuracy of heat transfer coefficient of spiral tube annular space refrigerant is one of the key parameters necessary to study the condensation heat transfer performance of a new type of alternative refrigerant. Even so, the thermal and physical properties of R134a and R22 are not the same. Therefore, it is very important to study the heat transfer performance and pressure drop characteristics of R134a for improving the original system equipment, researching and developing new system equipment. The total heat transfer capacity, total heat transfer coefficient, suction and exhaust pressure of the compressor, input power of the system, heat production coefficient and heat production coefficient of the condenser are tested. The total heat transfer capacity, total heat transfer coefficient, suction and exhaust pressure of the compressor, and the input power of the system are measured when the inlet water temperature of the condenser is constant under the condition of DC steady state. (1) When the water flow is circulated, the inlet water flow of the condenser is constant, and with the inlet water temperature rising, the total heat transfer coefficient of the condenser is changed. When the inlet water temperature of the spiral tube condenser increases from 25.2 C to 63 C, the total heat transfer coefficient decreases. The total heat transfer coefficient increases from 1184.12 W / (m2 K) to 1643.21 W / (m2 K), the suction pressure rises from 0.34 MPa to 0.38 MPa, the exhaust pressure rises from 0.77 MPa to 2.00 MPa, the input power rises from 1040 W to 2100 W, the thermal performance coefficient COP decreases from 4.4 to 1.2, and the heat production decreases from 1387.83 W to 667.14 W. W. (2) When the inlet water temperature of the condenser is constant, the total heat transfer capacity and total heat transfer coefficient of the condenser increase with the increase of the inlet water flow rate, while the suction, exhaust pressure and input power of the compressor decrease. The heat production and heating coefficient of the heat pump system increase with the increase of the inlet water flow rate. When the inlet flow rate of the spiral tube condenser increases from 1.19 m3/h to 2.16 m3/h, the total heat transfer capacity of the condenser increases from 4025.72 W to 7565.71 W, the total heat transfer coefficient increases from 1472.03 W /(m2.K) to 3956.29 W /(m2.K), the suction pressure decreases from 0.36 MPa to 0.35 MPa, the exhaust pressure decreases from 1.38 MPa to 1.27 MPa, and the system input power decreases from 1488.67 W to 1 956.29 W /(m2.K). At 1423.75W, the COP of the system increases from 2.5 to 3.0, and the heat of the system increases from 986.90W to 1087.06W. (3) When the inlet water temperature of the condenser is constant, the total heat transfer capacity and the total heat transfer coefficient of the spiral sleeve condenser increase with the increase of the inlet water flow rate. When the inlet water temperature is kept at 22 C and the inlet water flow rate of the spiral tube condenser increases from 0.26 m3/h to 0.71 m3/h, the total heat transfer capacity of the spiral tube condenser increases from 3614.24 W to 4165.96 W, the total heat transfer coefficient increases from 1999.03 W /(m2.K) to 2835.92 W /(m2.K), and the suction pressure of the compressor increases from 0.32 MP. A decreases to 0.30 MPa, the exhaust pressure decreases from 0.84 MPa to 0.62 MPa, and the input power of the system decreases from 1040 W to 920 W. In this paper, the heat transfer performance of the spiral tube condenser and the operation performance of the heat pump are studied experimentally and theoretically. The research is expected to provide reference for optimum design of heat exchanger and energy-saving operation of heat pump water heater in refrigerant substitution.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU822

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