Refrigeration (FEU)

1. A Carnot cycle operates between -8℃ and 18℃. Find the coefficient of performance.

• 4.56

• 8.43

• 6.34

• 10.19

2. A refrigeration system operates on the reversed Carnot cycle. The minimum and maximum temperatures are -25℃ and 72℃ , respectively. If the heat rejected at the condenser is 6000 kJ/min. Find the power input required.

• 1286.957 kJ/min

• 1486.957 kJ/min

• 1686.957 kJ/min

• 1886.957 kJ/min

3. A refrigerating system operates on the reversed Carnot cycle. The higher temperature of the refrigerant in the system is 120 ℉ and the lower is 10 ℉. The capacity is 20 tons. Neglect losses. Determine the network in BTU/min.

• 916.21  kJ/min

• 936.21  kJ/min

• 956.21  kJ/min

• 976.21  kJ/min

4. Determine the heat extracted from 2000 kg of water from 25℃ to ice at -10℃.

• 921 150 kJ

• 941 150 kJ

• 961 150 kJ

• 981 150 kJ

5. An ice plant produces 20 tons of ice per day at -15 ℃ from water at 25 ℃. If miscellaneous losses are 12% of the freezing and chilling load, calculate the refrigeration capacity of the plant in tons of refrigeration.

• 28.13

• 38.13

• 31.50

• 41.50

6. Five hundred kilogram of poultry enter a chiller at 8C and are frozen and chilled to a final temperature of – 18C for storage in 15 hours. The specific heat above and below freezing are 3.18 kJ/kgC and 1.55 kJ/kgC respectively. The latent heat is 246 kJ/kg and the freezing temperature is – 5C. Compute the product load.

• 2.25 kW

• 2.45 kW

• 2.65 kW

• 2.85 kW

7. Compute the heat to be removed from 110 kg of lean beef if it were to be cooled from 20C to 4C, after which it is frozen and cooled to – 18C. Specific heat of beef above freezing is given as 3.23 kJ/kgC and below freezing is 1.68 kJ/kgC, freezing point is – 2.2C and the latent heat of fusion is 233 kJ/kg.

• 32,438 kJ

• 34,438 kJ

• 36,438 kJ

• 38,438 kJ

8. Fish weighing 11,000 kg with a temperature of 20 ℃ is brought to a cold storage and which shall be cooled to -10 ℃ in 11 hours. Find the required plant refrigerating capacity in tons of refrigeration if the specific heat of fish is 0.7 kCal/kg∙℃ above freezing and 0.30 kCal/kg℃ below freezing point which is -3 ℃. The latent heat of freezing is 55.5 kCal/kg.

• 25.26

• 15.26

• 14.38

• 24.37

9. Magnolia dairy products plant must cool 4000 gallons of fresh milk received from the farm per day from an initial temperature of 80 ℉ to a temperature of  38 ℉ in 5 hours. If the density of milk is 8.6 lb/gal; specific gravity is 1.03 and specific heat is 0.935 Btu/lbR, what must be the capacity of the refrigerating machine in tons?

• 12.515

• 22.515

• 32.515

• 16.515

10. A creamery must cool 20,000 liters of milk received each day from initial temperature of 29 ℃ to a final temperature of 2 ℃ in 5 hours. If refrigeration losses amount of 10 percent of the cooling load, what must be the capacity of the refrigerating machine? Note: Specific heat of milk is 3.9 kJ/kg-K and SG=1.05.

• 38.5 TOR

• 36.5 TOR

• 37.5 TOR

• 39.5 TOR