Saturated propane vapor at 2:00 102 psia is fed to a well-insulated heat exchanger at a

Chapter 8, Problem 8.65

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Saturated propane vapor at 2:00 102 psia is fed to a well-insulated heat exchanger at a rate of 3:00 103 SCFH (standard cubic feet per hour). The propane leaves the exchanger as a saturated liquid (i.e., a liquid at its boiling point) at the same pressure. Cooling water enters the exchanger at 70F, flowing cocurrently (in the same direction) with the propane. The temperature difference between the outlet streams (liquid propane and water) is 15F. (a) What is the outlet temperature of the water stream? (Use the Antoine equation.) Is the outlet water temperature less than or greater than the outlet propane temperature? Briefly explain. (b) Estimate the rate (Btu/h) at which heat must be transferred from the propane to the water in the heat exchanger and the required flow rate (lbm/h) of the water. (You will need to write two separate energy balances.) Assume the heat capacity of liquid water is constant at 1.00 Btu/(lbmF) and neglect heat losses to the outside and the effects of pressure on the heat of vaporization of propane.