"Water is heated by hot air in a heat exchanger. The ow rate of the water is 12 kg s and that of the air is 1 kg s. The water enters at 4C. and the air enters at 4oC The overall heat transfer coefcient of the heat exchanger is 275 "W tn2 K based on a surface area of 14 in}. Determine the effectiveness of the heat exchanger if it is: {a} A parallel-ow type {b} A crosson' type (both uids tunnixed). Then calculate the heat transfer rate for the two types of heat exchangers described and the outlet temperatures of the hot and cold uids for the conditions given