It is desired to freeze 10,000 loaves of bread each weighing 0.75 kg from an initial room temperature of 18°C to a final temperature of -18°C. The bread-freezing operation is to be carried out in an air-blast freezing tunnel. It is found that the fan motors are rated at a total of 80 horsepower and measurements suggest that they are operating at around 90% of their rating, under which conditions their manufacturer’s data claims a motor efficiency of 86%. If 1 ton of refrigeration is 3.52 kW, estimate the maximum refrigeration load imposed by this freezing installation assuming that fans and motors are all within the freezing tunnel insulation and the heat-loss rate from the tunnel to the ambient air has been found to be 6.3 kW.

Extraction rate from freezing bread (maximum) = 104 kW

A textile dryer is found to consume 4 m3 / hr of natural gas with a calorific value of 800 kJ/mole. If the throughput of the dryer is 60 kg of wet cloth per hour, drying it from 55% moisture to 10% moisture, estimate the overall thermal efficiency of the dryer taking into account the latent heat of evaporation only.

Assuming the natural gas to be at standard temperature and pressure at which 1 mole occupies 22.4 liters and Latent heat of evaporation = 2257 kJ/K.

Explore topic-wise MCQs in Bioprocess Engineering Questions and Answers.

This section includes 5 Mcqs, each offering curated multiple-choice questions to sharpen your Bioprocess Engineering Questions and Answers knowledge and support exam preparation. Choose a topic below to get started.

1.	How much work can be obtained from an adiabatic, continuous-flow turbine, if steam at 60 bar and 500oC is used and the outlet stream is at 1 bar and 400oC?
A.	-144 kJ/kg
B.	-155 kJ/kg
C.	-166 kJ/kg
D.	-177 kJ/kg
Answer» B. -155 kJ/kg

Discussion

2.	Concentrated fermentation liquid containing 20% (w/w) gluconic acid from an evaporator has a flow rate of 2000 kg/h and a temperature 90 °C. It needs to be cooled to 6 °C in a heat exchanger with cooling water. The cooling water has a flow rate 2700 kg/h and an initial temperature 2 °C. If the cooling water leaves the heat exchanger at 50 °C, what is the rate of heat loss from gluconic acid solution to the surroundings? Assume the heat capacity of gluconic acid is 0.35 cal/g-°C-1.
A.	69390.84 kJ/h
B.	65780.56 kJ/h
C.	67890.67 kJ/h
D.	65432.10 kJ/h
Answer» B. 65780.56 kJ/h

Discussion

3.	It is desired to freeze 10,000 loaves of bread each weighing 0.75 kg from an initial room temperature of 18°C to a final temperature of -18°C. The bread-freezing operation is to be carried out in an air-blast freezing tunnel. It is found that the fan motors are rated at a total of 80 horsepower and measurements suggest that they are operating at around 90% of their rating, under which conditions their manufacturer’s data claims a motor efficiency of 86%. If 1 ton of refrigeration is 3.52 kW, estimate the maximum refrigeration load imposed by this freezing installation assuming that fans and motors are all within the freezing tunnel insulation and the heat-loss rate from the tunnel to the ambient air has been found to be 6.3 kW.
A.	Extraction rate from freezing bread (maximum) = 104 kW
B.	46 tons of refrigeration
C.	40 tons of refrigeration
D.	56 tons of refrigeration
E.	50 tons of refrigeration
Answer» B. 46 tons of refrigeration

Discussion

4.	A textile dryer is found to consume 4 m3 / hr of natural gas with a calorific value of 800 kJ/mole. If the throughput of the dryer is 60 kg of wet cloth per hour, drying it from 55% moisture to 10% moisture, estimate the overall thermal efficiency of the dryer taking into account the latent heat of evaporation only.
A.	Assuming the natural gas to be at standard temperature and pressure at which 1 mole occupies 22.4 liters and Latent heat of evaporation = 2257 kJ/K.
B.	40%
C.	50%
D.	58%
E.	48%
Answer» E. 48%

Discussion

5.	If 35,000kg of whole milk containing 4% fat is to be separated in a 6 hour period into skim milk with 0.45% fat and cream with 45% fat, what are the flow rates of the two output streams from a continuous centrifuge which accomplishes this separation? (Basis 1 hour’s flow of whole milk.)
A.	5678 kg/hr
B.	5368 kg/hr
C.	2567 kg/hr
D.	2578 kg/hr
Answer» C. 2567 kg/hr

Discussion

Explore topic-wise MCQs in Bioprocess Engineering Questions and Answers.

How much work can be obtained from an adiabatic, continuous-flow turbine, if steam at 60 bar and 500oC is used and the outlet stream is at 1 bar and 400oC?

If 35,000kg of whole milk containing 4% fat is to be separated in a 6 hour period into skim milk with 0.45% fat and cream with 45% fat, what are the flow rates of the two output streams from a continuous centrifuge which accomplishes this separation? (Basis 1 hour’s flow of whole milk.)