Question

Design Problem Design a small chiller room 2.35 m wide by 6 m long and 2.38 m high that is to be used to chill and store a food product. The chiller is to be loaded with 60 buckets of the food product at 23 °C which needs to be cooled down to 3 °C within 24 hours using air at 1 °C, with a heat transfer coefficient of 36 W m2 K Tasks 1. Calculate the peak refrigeration loading in kW (i.e. all sixty buckets right at the start of the chilling process), assuming the food product enters at a uniform temperature of 23 °C if the buckets are each 30 cm in diameter and 50 cm high. Calculate the average refrigeration load (in kW) to cool the full load assuming it has the same thermal properties as water (you may ignore the thermal mass of the buckets themselves, and the chiller walls) Calculate the time required for the centre temperature of an individual bucket to reach 3 °C from an initial uniform temperature of 23 °C assuming the air around it is maintained at 1 °C, which has an average heat transfer coefficient of 36 W m2 K-1 If the time calculated in Part 3 is not equal to 24 hours, what significance does that have? Calculate the thickness of insulation required to keep heat loss through the container walls below 15 W/m2, assuming the thermal conductivity of the insulation is 0.04 W m K-1, and the inside and outside heat transfer coefficients are 36 W m2 K1 and 25 W m2 K1 respectively when the air inside is 0.5 °C and the air outside is 30 °C Based on your calculations from Parts 1 to 5 specify a refrigeration system (i.e compressor power, heat exchange surface area etc.) that will be suitable for the task. You may specify actual commercial equipment that will achieve the required cooling, or you my just determine the required specifications You are not required to calculate costs, but you should discuss any assumptions you have made in this design process 2. 3. 4. 5. 6. 7.

Answer 1

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