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7–115 Air (Cp 1.005 kJ/kg · °C) is to be preheated by hot
exhaust gases in a cross-flow heat exchanger before it enters the
furnace. Air enters the heat exchanger at 95 kPa and 20°C at a
rate of 1.6 m3/s. The combustion gases (Cp 1.10 kJ/kg · °C)
enter at 180°C at a rate of 2.2 kg/s and leave at 95°C. Determine
the rate of heat transfer to the air, the outlet temperature of the
air, and the rate of entropy generation.
7–116 A well-insulated, shell-and-tube heat exchanger is
used to heat water (Cp
4.18 kJ/kg · °C) in the tubes from
20°C to 70°C at a rate of 4.5 kg/s. Heat is supplied by hot oil
2.30 kJ/kg · °C) that enters the shell side at 170°C at
a rate of 10 kg/s. Disregarding any heat loss from the heat
exchanger, determine (a) the exit temperature of the oil and
(b) the rate of entropy generation in the heat exchanger.
4.5 kg/s Brine
140°C FIGURE P7–116 60°C FIGURE P7–111
7–112 An adiabatic heat exchanger is to cool ethylene glycol
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This document was uploaded on 11/28/2012.
- Spring '09