word of warning: this homework assignment uses the English system of units. In t
ID: 2088580 • Letter: W
Question
word of warning: this homework assignment uses the English system of units. In this system, the unit o energy is a BTU (British Thermal Unit), and the specific heat of water is 1 BTU/(b*F). Which is to say: it take BTU of heat energy to raise the temperature of 1 pound of water 1 degree Fahrenheit. 1. When designing a house to be built in a climate that requires heating, a heat load calculation is carried out for each room of the house. The calculated heat load is used to size the heating system (i.e. the devices that generate and then distribute the heat to the rooms). Suppose that the heat load of a particular bedroom in a house is 3268 BTU/hr when the outdoor temperature is-30F and the interior temperature is 70°F. In this house, the heat is proved by baseboard radiators, such that the temperature of the water at the inlet to the radiator is 173°F, while at the exit it is 170°F, what is the required flow rate of water through the radiator in gallons per minute in order to meet the required heat load? Give your answer in gallons per minute. A gallon of water at 180°F weighs about 8.1 pounds.Explanation / Answer
Given,
Specific heat of water, c = 1BTU/ (lb*F)
Required heat load, q? = 3268 BTU/hr
Temperature difference between inlet and outlet of radiator, ?T = 178 – 170 = 8°F
Let, m = mass flow rate of water through the radiator in lb/hr
The heat to be transferred to the bed room to maintain the specified temperature is given by:
q? = m×c×?T
=> 3268 = m×1×8
=> m = 408.5 lb/hr
? The required flow rate of water through the radiator = 408.5 / 8.1 gallons/hr = 50.43 gallons/hr = 50.43/60 gallons/minute = 0.84 gallons/minute
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