Question

(Please show your work) (1 kwh = 3400 BTU’s 1 gallon = 8 pounds of water) The water coming into a dishwasher from a water heater is 50 degrees F. It has to be heated to 100 degrees. The dishwasher uses 10 gallons of water and .5 kwh of electrical energy to operate. How much total energy in BTU’s is needed to heat the water and run the dishwasher?

Answer 1

Answer:

5700 BTU

Step-by-step explanation:

Data provided in the question:

1 kwh = 3400 BTU’s

1 gallon = 8 pounds of water

Initial temperature = 50°F

Final temperature = 100°F

Water used by dishwasher = 10 gallons

Electrical energy used = 0.5 kwh

Now,

Water used in pounds = 10 × 8 = 80 lb

Total electrical energy used in BTU = 0.5 × 3400 BTU     [ as 1 kwh = 3400 BTU]

Total electrical energy used in BTU = 1700 BTU

Energy used by water = Water used by dishwasher × Change in temperature × Specific heat of water

[  Specific heat of water = 1 BTU / °F.lb ]

Thus,

Energy used by water = 80 × 1 × ( 100 - 50 )

= 4000 BTU

Hence,

Total energy used = 1700 BTU + 4000 BTU = 5700 BTU