The heat exchanger design and choice

The heat exchanger design and choice

According to the heat pump units directly contact with raw water whether heat exchanger, the original water source heat pump system can be divided into direct type the water source &heat pump system and the water source heat pump system JianJieShi. Direct type the original water heat pump system heat pump units within the direct contact heat exchanger and the raw water, although the system equipment of low investment, but early corrosion and jams easily unit heat exchanger. JianJieShi sewage-source heat pump system through the raw water recycling raw water in the heat exchanger, raw water not enter the heat pump unit, to avoid the raw water chillers and congestion, although investment corrosion increased, but the system equipment operation, this paper mainly JianJieShi reliable in the water source &heat pump system as the research object of raw water heat exchanger. This paper selects the two kinds of heat exchanger subjects, one kind is copper plate heat exchanger, such as immersion in the original water tank, the water in the heat tube plate circulating outside of the tube, and raw water in hot,. Raw water quality complex, the subject of this star hotel group of raw water water samples for the tests, the microbes are caused by the original water copper corrosion of important factors, because algae and bacteria most appropriate growth conditions is 30 ℃ ~ 40 ℃ temperature, pH 5 · 5 ~ 8, 9, and the water system is precisely what is the condition of the body. The algae and contribute to the production of slime, slime dirt deposited in equipment, in biological membrane/metal interface produce a different from the special environment of ontology solution, in this special environment microorganisms and metal with a lot of complex chemical reactions, thus causes corrosion. And the water dissolved H2S, it can generate black role with copper, accelerated the heat exchanger CuS copper pitting corrosion of the hotel. The water characteristics, the original pool of water level caused by is not fixed, when the hotel for a little while and displacement reduce water consumption, the original pool water level drops, part of the heat exchanger will be exposed to air, copper in the wet air oxidation easily in the produce, and the atmosphere p. nitrides, sulfide and particles can to copper corrosion caused by heat exchanger. Because the raw water and air is on the heat exchanger cause corrosion, heat exchanger should use corrosion resistant material, good materials can reduce the possibility of corrosion of the heat exchanger and the subsequent decline and other operation problem, so this paper and designed a kind of finned tube heat exchanger, fluctuation of total four layers finned tube, a parallel operation, the four layers of finned tube and fin do plastic plating processing, on copper tube and aluminum fin surface, with a layer of anticorrosion material, can be a very good protection of heat exchanger in raw water from corrosion, solve the problem of raw water heat exchanger corrosive, but at the same time it brought new problems, coating the coefficient of thermal conductivity is low, and the heat transfer effect that heat exchanger than did not add to poor before coating. In order to test anticorrosive finned tube heat exchanger and the heat exchange performance, this paper builds the small heat pump test bench to fin tube heat exchanger performance parameters on the experimental results, and with copper plate heat exchanger were compared.

换热器的设计与选择
    根据热泵机组换热器是否直接与原水接触,原水源热泵系统可分为直接式原水源热泵系统和间接式原水源热泵系统.直接式原水源热泵系统热泵机组内的换热器与原水直接接触,虽然系统设备初投资低,但机组换热器极易腐蚀和堵塞.间接式污水源热泵系统通过原水换热器回收原水中的热量,原水不进入热泵机组,避免了原水对机组的腐蚀和堵塞,虽然投资增加,但系统设备运行可靠,本文主要以间接式原水源热泵系统的原水换热器为研究对象.
    本文选取了两种换热器作为实验对象,一种是铜盘管换热器,如沉浸于原水箱中,水在换热盘管内循环流动,与管外的原水进行换热,.
             
    原水水质复杂,本课题小组对该星级宾馆的原水水样进行了检测,原水中的微生物是造成铜腐蚀的重要因素,因为藻类和细菌最适宜的生长条件是温度30℃~40℃,pH 5·5~8·9,而水系统恰恰是在此条件下运行的.藻类及其尸体助长了粘泥的产生,粘泥污垢在设备上沉积,在生物膜/金属界面上产生一个不同于本体溶液的特殊环境,在这种特殊环境中各种微生物与金属进行着大量复杂的化学反应,从而导致腐蚀.还有水中溶解的H2S,它能与铜作用生成黑色的CuS,加速了铜换热器的点蚀.由宾馆的用水特性所致,原水池的水位不是固定不变的,当宾馆用水量少时,排水量减少,原水池水位下降,换热器的一部分就会暴露在空气中,铜在潮湿的空气中极易被氧化产生铜绿,同时大气中的氮化物、硫化物和粒子都能对铜换热器造成腐蚀.
            
    由于原水及空气都会对换热器造成腐蚀,换热器应使用耐腐蚀材料,良好的选材能减少腐蚀的可能性和随之而来的换热器下降及其它运行问题,因此本文又设计了一种翅片管式换热器,上下共四层翅片管,四层呈并联运行,对翅片管及翅片都做了镀塑处理,在铜管和铝翅片表面镀了一层防腐材料,可以很好地保护换热器在原水中不受腐蚀,解决了原水换热器的腐蚀性问题,但同时又带来了新的问题,镀层的导热系数很低,使得换热器的换热效果比未加镀层前要差.
             
    为了检验防腐翅片管换热器的换热性能,本文搭建了小型热泵实验台对翅片管换热器的性能参数进行了试验测定,并与铜盘管式换热器进行了对比.