A 200-1itre stirred fermenter contains a batch culture of Bacillus subtilis bacteria at 28⁰C Air at 20⁰C is pumped into the vessel at a rate of 1 vvm; (vvm stands for volume of gas per volume of liquid per minute). The average pressure in the fermenter is 1 atm. The volumetric flow rate of off-gas from the fermenter is measured as 189 l min^-1. The exit gas stream is analysed for oxygen and is found to contain 20.1% 0₂. The dissolved-oxygen concentration in the broth is measured using an oxygen electrode as 52% air saturation. The solubility of oxygen in the fermentation broth at 28⁰C and 1 atm air pressure is 7.8 x 10^-3 kg m^-3. Calculate the oxygen transfer rate_____________

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#Question id: 15644

#Section 4: Fundamentals of Biological Engineering

Based on the flow behavior of fluids depicted in the following figure. choose the correct option.

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#Question id: 15645

#Section 4: Fundamentals of Biological Engineering

An aluminium pot contains water that is kept steadily boiling (100 °C). The bottom surface of the pot, which is 0.012 m thick and 1.5 x 10⁴ mm² in area, is maintained at a temperature of 102 °C by an electric heating unit. Find the rate at which heat is transferred through the bottom surface. Given k= 235 W.m^-1.K^-1

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#Question id: 15646

#Section 4: Fundamentals of Biological Engineering

The quantity of heat required to evaporate 1 kg of a saturated liquid is called

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#Question id: 15647

#Section 4: Fundamentals of Biological Engineering

A liquid stream is cooled from 80°C to 30°C in a double pipe heat exchanger as illustrated below: 

Fluid flowing counter currently with this stream is heated from 15°C to 30°C. Calculate the log mean temperature difference. 

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#Question id: 15648

#Section 4: Fundamentals of Biological Engineering

The main function of baffles in a bioreactor are

P. to prevent a vortex

Q. to increase aeration

R. to reduce interfacial area of oxygen transfer

S. to reduce aeration rate

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#Question id: 15649

#Section 4: Fundamentals of Biological Engineering

A bacterial culture having a specific oxygen uptake rate of 5 mmol O2 (g DCW)⁻¹ h⁻¹ is being grown aerobically in a fed-batch reactor. The maximum value of the volumetric oxygen transfer coefficient is 0.18 s⁻¹ for the stirred tank bioreactor and the critical dissolved oxygen concentration is 20% of the saturation concentration (8 mg L⁻¹). The maximum density to which the cells can be grown in the fed-batch process, without the growth being limited by oxygen transfer, is approximately