In a chemical plant, a certain chemical is heatedby hot water supplied by a natural gas furnace. The hot water(cp= 4180 J/kg·K) is then discharged at 60°C at a rate of 8 kg/min. The plant operates 8 h a day, 5 days a week, 52 weeks ayear. The furnace has an efficiency of 78 percent, and the costof the natural gas is $1.00 per therm (1 therm = 105,500 kJ).The average temperature of the cold water entering the furnacethroughout the year is 14°C. In order to save energy, it isproposed to install a water-to-water heat exchanger to preheatthe incoming cold water by the drained hot water. Assumingthat the heat exchanger will recover 72 percent of the availableheat in the hot water, determine the heat transfer rating of theheat exchanger that needs to be purchased and suggest a suitabletype. Also, determine the amount of money this heat exchangerwill save the company per year from natural gas savings.
Heat Exchangers
Heat exchangers are the types of equipment that are primarily employed to transfer the thermal energy from one fluid to another, provided that one of the fluids should be at a higher thermal energy content than the other fluid.
Heat Exchanger
The heat exchanger is a combination of two words ''Heat'' and ''Exchanger''. It is a mechanical device that is used to exchange heat energy between two fluids.
In a chemical plant, a certain chemical is heated
by hot water supplied by a natural gas furnace. The hot water
(cp= 4180 J/kg·K) is then discharged at 60°C at a rate of 8 kg/
min. The plant operates 8 h a day, 5 days a week, 52 weeks a
year. The furnace has an efficiency of 78 percent, and the cost
of the natural gas is $1.00 per therm (1 therm = 105,500 kJ).
The average temperature of the cold water entering the furnace
throughout the year is 14°C. In order to save energy, it is
proposed to install a water-to-water heat exchanger to preheat
the incoming cold water by the drained hot water. Assuming
that the heat exchanger will recover 72 percent of the available
heat in the hot water, determine the heat transfer rating of the
heat exchanger that needs to be purchased and suggest a suitable
type. Also, determine the amount of money this heat exchanger
will save the company per year from natural gas savings.
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