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Thermodynamics and engines (A-level only)

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Question 9

An active cooling vest for emergency personnel uses a thermoelectric Peltier module to keep the inner lining cool. Under typical operating conditions in a hot environment, the inner cold side of the module is maintained at 14 ∘C14\ ^\circ\text{C}14 ∘C, whilst the outer heat sink (the hot side) is at 54 ∘C54\ ^\circ\text{C}54 ∘C.

Manufacturer specifications for the module under these operating temperatures state that:

  • the rate at which heat energy is rejected from the hot side is 160 W160\text{ W}160 W
  • the electrical power supplied to the module from a wearable battery pack is 75 W75\text{ W}75 W
a.

An engineer claims that the actual coefficient of performance (COP) of this thermoelectric cooler is less than 20%20\%20% of the COP of an ideal refrigerator operating between the same two temperatures.

Evaluate whether the engineer's claim is valid.

[4]
b.

Suggest why a low COP is acceptable for this wearable cooling vest.

[4]

Thermodynamics and engines (A-level only) Questions

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