(a) Two different potatoes are baked in an oven at a temperature of 200C with air...

 

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(a) Two different potatoes are baked in an oven at a temperature of 200C with air containing 20% steam circulating around them. You can assume that the potatoes can be modelled as spheres of diameters 4 cm and 8 cm suspended in the air. The heat transfer coefficient between air and the small potato is 18 W m2 K-1 and between air and the large potato is 12.5 W m2 K-1 (b) (i) Name the mechanisms of heat transfer to, and inside the potatoes and for each of these mechanisms write the equation relating the heat flux to the temperature, name the proportionality coefficients in these equations and give their units. (ii) Calculate the time necessary to heat the potatoes from 20C to 100C and the amount of energy supplied to each potato. Water is cooled as it flows through a pipe surrounded by air. It is suggested to increase the intensity of cooling by using fins. (i) Where would you attach the fins to achieve this: on the water side or on the air side? Justify your answer. (ii) What parameters should you consider when designing those fins? (iii) Explain why fins should be tightly attached to the surface. (a) Two different potatoes are baked in an oven at a temperature of 200C with air containing 20% steam circulating around them. You can assume that the potatoes can be modelled as spheres of diameters 4 cm and 8 cm suspended in the air. The heat transfer coefficient between air and the small potato is 18 W m2 K-1 and between air and the large potato is 12.5 W m2 K-1 (b) (i) Name the mechanisms of heat transfer to, and inside the potatoes and for each of these mechanisms write the equation relating the heat flux to the temperature, name the proportionality coefficients in these equations and give their units. (ii) Calculate the time necessary to heat the potatoes from 20C to 100C and the amount of energy supplied to each potato. Water is cooled as it flows through a pipe surrounded by air. It is suggested to increase the intensity of cooling by using fins. (i) Where would you attach the fins to achieve this: on the water side or on the air side? Justify your answer. (ii) What parameters should you consider when designing those fins? (iii) Explain why fins should be tightly attached to the surface.

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The question seems to involve thermal processes and heat transfer mechanisms Lets address each part one by one ai Mechanisms of heat transfer to and inside the potatoes There are three primary mechani... View the full answer