overall heat transfer coefficient of condensor

Hi,

please someone help me in designing a condenser for an a/c. I am asked to design a condenser in which tube area is to be calculated (Q, LMTD are found, but overall heat transfer coeficient -U is given as 5 and i dont know the source). Can anyone help me to find the overall heat transfer coefficient of a tube and fin type condenser of a refrigerator (cross flow). Is there any data book to directly find this from the parameters. Or if finding by calculation how can i get the values of convection heat transfer coefficient of inside and outside of the tube (from data book?). Thankyou in advance

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There are a number of factors that control U in a coil. One is the Reynolds number associated with the speed of the air across the coil. The more turbulent it is, the more air molecules that are in contact with the metal surface and therefore, the better the heat transfer ability. Another is the type of material the coil is made from. Copper tube/ copper finned coils are marginally better than copper tube/ aluminium finned coils.

Coil manufacturers do a lot of testing with their materials and designs to establish these values for their calculation software packages and are generally not inclined to give up their hard-won intellectual property. You may find it difficult to get accurate figures for these.