Condensers and Cooling Towers

A condenser in a vapor compression cycle accepts the hot, high-pressure gas from the compressor, and cools it to remove first the superheat, and then the latent heat, so that the refrigerant will condense back to a liquid. In addition, the liquid is usually slightly subcooled. The provision of separate oil cooler will reduce condenser load by the amount of heat lost to the oil and removed in the oil cooler. This is of special note with oil-injected screw compressors, where a high proportion of the compressor energy is taken away in the oil. This proportion varies with the exact method of oil cooling, and figures should be obtained from the compressor manufacturer for a particular application. Small water-cooled condensers may comprise two concentric pipes, the refrigerant being in either the inner tube or the annulus. Configurations may be straight, with return bends or headers, or coiled. The double-pipe condenser is circuited in counterflow to get the most subcooling, since the coldest water will meet the outgoing liquid refrigerant. Larger sizes of water-cooled condenser require closer packing of the tubes to minimize the overall size, and the general form is shell-and-tube, having the water in the tubes.