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Old Nov 16th 2017, 09:29 AM   #1
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Lengthy Thermodynamics Cycle Problem

I know I must have already attempted to solve this problem, but I am overwhelmed with finals so I'd be happy to PayPal someone to complete this problem. Please, please help. My email is vodkamakesmesober@yahoo.com, email me if you are willing to help! Thank you.

You design custom refrigeration units for executive and private jets. Clients enlisting your services often have unusual habits and needs; they consist of entertainers, athletes, royalty, oil tycoons, and others who tend to spend money extravagantly. For this project, you will be designing a refrigeration unit. You will be able to frame the problem as you would like – you can choose your client’s background, and what uses they would have for their refrigerator. Money is no object, but because it will be used in an aircraft, size, mass, and energy efficiency are important factors to consider.

Refrigeration Cycle Design:

You will be able to design your refrigeration cycle any way you decide best meets your client’s needs, with the following restrictions:

1. Your refrigerator must run a Carnot or vapor-compression refrigeration cycle.

2. Your working fluid must be either Refrigerant-134a or Refrigerant-22 (tables for R-22 are on the CD that comes with the textbook).

3. You must use the ambient air (20°C) inside the aircraft cabin as your high temperature reservoir.

4. You must use one of the provided insulation types (see below).


Compressor: Mass: 2.750 kg + 0.025 kg per watt of power input

Size: 4.75 cm3 per watt of power input

Turbine: Mass: 2.750 kg + 0.025 kg per watt of power output

Size: 4.75 cm3 per watt of power output

Expansion Valve: Negligible size and mass

Heat Exchangers/Piping: Depends on many factors, but variation is not often extreme; we will assume a mass of 5 kg and a size of 0.25 m3 for each heat exchanger (condenser and evaporator). This includes the mass of the working fluid. If your refrigerator is particularly large or small then these values will not be accurate, but use them anyway for the sake of this exercise.

1/16” Stainless Mass: 550 g/m2

Steel Casing (cosmetic): Size: Negligible


Type, Density (kg/m3), Thermal Conductivity (W/m·K), Notes

Polystyrene Foam (Type I), 10, .57, Flammable

Polystyrene Foam (Type II), 12, .44, Flammable

Polystyrene Foam (Type III), 15, .37, Flammable

Polystyrene Foam (Type IV), 20, .34, Flammable

Polystyrene Foam (Type V), 25, .33, Flammable

Polyurethane Foam, 64, .12

Fiberglass (blown), 10, .44, Permeable to Moisture

Strategy & Hints:

This is most easily completed if you follow these steps in approximately this order:

1. Define client needs, and choose fridge temp (low temp reservoir)

2. Choose fridge shape and storage size

3. Choose insulation and thickness; calculate heat transfer rate into the fridge.

4. Choose cycle and choose high and low cycle temperatures

5. Choose working fluid and cycle states in specific (per kg) terms

6. Calculate heat transfer and work values in specific (per kg) terms

7, Using the specific heat transfer of your cycle and the needed heat transfer rate of your fridge, calculate the necessary mass flow rate. Make sure the result is reasonable; if not, go back and re-do step 3 or step 5.

8. Calculate all work and heat transfer rates, and coefficient of performance.

9. Calculate total size and mass of the fridge.
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