The thermal characteristics of a small, dormitory refrigerator are determined by performing two separate experiments, each with the door closed and the refrigerator placed in ambient air at T ∞ = 25 ° C . In one ease, an electric heater is suspended in the refrigerator cavity, while the refrigerator is unplugged. With the heater dissipating 20 W, a steady-state temperature of 90°C is recorded within the cavity. With the heater removed and the refrigerator now in operation, the second experiment involves maintaining a steady-state cavity temperature of 5°C for a fixed time interval and recording the electrical energy required to operate the refrigerator. In such an experiment for which steady operation is maintained over a 12-hour period, the input electrical energy is 125,000 J. Determine the refrigerator's coefficient of performance (COP).
The thermal characteristics of a small, dormitory refrigerator are determined by performing two separate experiments, each with the door closed and the refrigerator placed in ambient air at T ∞ = 25 ° C . In one ease, an electric heater is suspended in the refrigerator cavity, while the refrigerator is unplugged. With the heater dissipating 20 W, a steady-state temperature of 90°C is recorded within the cavity. With the heater removed and the refrigerator now in operation, the second experiment involves maintaining a steady-state cavity temperature of 5°C for a fixed time interval and recording the electrical energy required to operate the refrigerator. In such an experiment for which steady operation is maintained over a 12-hour period, the input electrical energy is 125,000 J. Determine the refrigerator's coefficient of performance (COP).
Solution Summary: The author explains how the refrigerator's coefficient of performance is 2.12. The expression for the heat transfer is given as, q=T_infty,i-
The thermal characteristics of a small, dormitory refrigerator are determined by performing two separate experiments, each with the door closed and the refrigerator placed in ambient air at
T
∞
=
25
°
C
.
In one ease, an electric heater is suspended in the refrigerator cavity, while the refrigerator is unplugged. With the heater dissipating 20 W, a steady-state temperature of 90°C is recorded within the cavity. With the heater removed and the refrigerator now in operation, the second experiment involves maintaining a steady-state cavity temperature of 5°C for a fixed time interval and recording the electrical energy required to operate the refrigerator. In such an experiment for which steady operation is maintained over a 12-hour period, the input electrical energy is 125,000 J. Determine the refrigerator's coefficient of performance (COP).
B
60 ft
WAB
AB
30%
:
The crane's telescopic boom rotates with the angular velocity w = 0.06 rad/s and
angular acceleration a = 0.07 rad/s². At the same instant, the boom is extending
with a constant speed of 0.8 ft/s, measured relative to the boom. Determine the
magnitude of the acceleration of point B at this instant.
The motion of peg P is constrained by the lemniscate curved
slot in OB and by the slotted arm OA. (Figure 1)
If OA rotates counterclockwise with a constant angular velocity of 0 = 3 rad/s, determine the magnitude of the velocity of peg P at 0 = 30°.
Express your answer to three significant figures and include the appropriate units.
Determine the magnitude of the acceleration of peg P at 0 = 30°.
Express your answer to three significant figures and include the appropriate units.
0
(4 cos 2 0)m²
B
A
5: The structure shown was designed to support a30-kN load. It consists of a boom AB with a 30 x 50-mmrectangular cross section and a rod BC with a 20-mm-diametercircular cross section. The boom and the rod are connected bya pin at B and are supported by pins and brackets at A and C,respectively.1. Calculate the normal stress in boom AB and rod BC,indicate if in tension or compression.2. Calculate the shear stress of pins at A, B and C.3. Calculate the bearing stresses at A in member AB,and in the bracket.
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