Chapter 5, Problem 5.48P

A heating system must maintain the interior of a building at TH = 20°C when the outside temperature is TC = 2°C. If the rate of heat transfer from the building through its walls and roof is 16.4 kW, determine the electrical power required, in kW, to heat the building using (a) electrical-resistance heating, (b) a heat pump whose coefficient of performance is 3.0, (c) a reversible heat pump operating between hot and cold reservoirs at 20°C and 2°C, respectively.

Determine the net power required to operate the heat pump, in kW. whose coefficient of performance of heat pump cycle is 2.5. the heat pump delivers energy to a dwelling at a heat transfer rate of 20 kW

To maintain a dwelling steadily at 68°F on a day when the outside temperature is 30°F, heating must be provided at an average rate of 300 Btu/min. Determine the electrical power required, in kW, to deliver the heating using: (a) electrical-resistance heating, (b) a heat pump whose coefficient of performance is 3.5, (c) a reversible heat pump operating between hot and cold reservoirs at 68°F and 30°F, respectively. Part A Determine the electrical power required, in kW, to deliver the heating using electrical-resistance heating. Wa i Save for Later kW Attempts: 0 of 4 used Submit Answer

1. Is a temperature difference necessary to operate a heat engine? State why or why not. 2. Definitions of efficiency vary depending on how energy is being converted. Compare the definitions of efficiency for the human body and heat engines. How does the definition of efficiency in each relate to the type of energy being converted into doing work? 3. Why-other than the fact that the second law of thermodynamics says reversible engines are the most efficient-should heat engines employing reversible processes be more efficient than those employing irreversible processes? Consider that dissipative mechanisms are one cause of irreversibility. 1. (a) What is the efficiency of a cyclical heat engine in which 75.0 kJ of heat transfer occurs to the environment for every 95.0 kJ of heat transfer into the engine? (b) How much work does it produce for 100 k) of heat transfer into the engine? 2. The engine of a large ship does 2.00×10°J of work with an efficiency of 5.00%. (a) How much heat…

A heat pump maintains a dwelling at 68°F. When operating steadily, the power input to the heat pump is 3 hp, and the heat pump receives energy by heat transfer from 55°F well water at a rate of 500 Btu/min. (a) Determine the coefficient of performance. (b) Evaluating electricity at $0.18 per kW · h, determine the cost of electricity in a month when the heat pump operates for 300 hours.

A heat pump supplies heat to a house at a rate of 30,000 kJ/hr. If the power consumed by the heat pump is 3 kW, determine the coefficient of performance of the heat pump.

A heat engine operates between thermal energy stores at 800 ° C and 20 ° C. Half of the power generated by the heat engine drives the Carnot heat pump, which is used to heat a house. While the interior temperature of the house is 22 ° C, the outside temperature is 2 ° C, the heat loss of the house is 62000 kJ / h. In these conditions, calculate the minimum heat that should be given to the heat machine per unit time as kW.

A closed system executes a series of processes for Wn = 80 BTU, U1 = 40 BTU and U2 = 5 BTU are given for each process. What is the value of heat in BTU? Is it added or rejected?

A silicon chip measuring 5 mm on a side and I mm in thickness is embedded in a ceramic substrate. At steady state, the chip has an electrical power input of 0.425 W. The top surface of the chip is exposed to a coolant whose temperature is 29°C. The heat transfer coefficient for convection between the chip and the coolant is 0.18 kw/m2 K. If heat transfer by conduction between the chip and the substrate is negligible, determine the surface temperature of the chip, in °R. Select one: O a. 714 O b. 353 O c. 396 O d. 635