Thermal Fluid Design Course Questions 1 through 4 refer to the use of a liquid C

Question

Thermal Fluid Design Course

Questions 1 through 4 refer to the use of a liquid CO2 reservoir to provide portable cooling. Consider a standard 20-lb (9.1 kg) cylinder as the reservoir. Such cylinders are readily available for use in commercial soda machines. Allowing the liquid to expand into a gas and eventually vent to the atmosphere provides an inexpensive, compact, portable source of cooling which (11)(?noi n(xxl í,() lx, conlloci od io a pow er sonce. The only downside i thai; it is a one-shot cooling solution that ceases to work when the liquid CO2 has been exhausted and the tank is empty

Explanation / Answer

3.

Mass m = 20 lb = 9.07 kg

From CO2 properties, at -10 deg C for saturated liquid we get internal energy u1 = 60.9 kJ/kg

From CO2 properties, at 30 deg C for saturated vapor we get internal energy u2 = 231 kJ/kg

Energy absorbed = m*(u2 - u1)

= 9.07 * (231 - 60.9)

= 1542.8 kJ ~ 103 kJ

4)

Power consumed in one hour = 1542.8 / (60 *60) = 0.426 kW = 426 W

COP = Heating load / Power input

3 = 426 / Power input

Power input = 142.8 W ~ 100 W

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