Research On Condensation Heat Transfer And Enhancement Of R22and Its Alternatives On Petal-Shaped Finned Tube Bundle

As the most widely used HCFCs refrigerants，the substitution problem of R22appears tobe imperative with the implementation of the Montreal International Treaty and theenhancement of human’s environmental protection consciousness. At present, R410A, R407Cand R134a have been recognized as the prospective candidates to replace R22. On the otherhand, the manufacturers of central air-conditioning and refrigeration equipment put forwardhigher requirements to the heart-transfer tube because of the target of energy-saving societyand the price of the raw materials. With unique three-dimensional finned structure, the copperpetal-shaped finned tube can effectively improve the heat transfer efficiency, and its economicperformance is excellent.In this paper, the condensation heat transfer performance of R22, R134a, R407C andR410A on the copper petal-shaped finned tube bundle were investigated at saturationtemperature of35℃and39℃. In contrast to copper smooth tube, this paper studies thecopper petal-shaped finned tube’s heat transfer efficiency and the tube bundle effect by meansof adjusting water flow rate and temperature. Also the relationship between the averageoverall heat transfer coefficient and water flow rate, the relationship between the condensationheat transfer coefficient and wall temperature, the relationship between the heat transfer andthermal resistance and the Reynolds number were studied on the same way. What’s more, theerror analysis of heat transfer coefficient of tube-inside, heat transfer coefficient oftube-outside and overall heat transfer coefficient have been carried out basing on the errorpropagation formula.The experiment results show that tube bundle effect has a great impact on thecondensation heat transfer performance of the four kinds of refrigerants. The condensationheat transfer coefficients decrease from the row1to row3at a given wall sub-cooling. Forcopper petal-shaped finned tube bundle, the average overall heat transfer coefficient of R22,R134a, R407C and R410A increase as the water flow rate increase, but it is a stable trend forthe copper smooth tube bundle. Under a certain temperature difference, the condensationHTCs of R22, R134a, R407C and R410A on copper petal-shaped finned tube bundle are9.82~10.93,7.64~9.82,9.39~11.31and5.52～5.58times than those on smooth tube bundle.By means of thermal resistance analysis, the ratio of average tube-inside thermalresistance to entire thermal resistance decrease as the Reynolds number increase and the ratioof average tube-outside thermal resistance to entire thermal resistance increase as the Reynolds number increase. When Reynolds number is in certain range, the two ratios haveapparent change as the Reynolds number changes, and when Reynolds number is more than acertain number, the change become subtle.