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Refrigeration

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by

Chris Nartey

on 27 May 2014

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Transcript of Refrigeration

Introduction
Refrigeration
Procedure
1. The system was turned on without the compressor function, with the fan speeds at an initial setting depending on the team preference.
2. The watt meter reading was recorded.
3. The compressor was turned on. The watt meter reading was recorded after 5-10 minutes, or until the gauges had settled on a consistent value.
4. The velocity of the air flow was recorded using the velocimeter, recording 3 values across the top of the condenser’s area of flow and 3 values across the bottom of the condenser’s area of flow, a total of 6 recorded values. This process was repeated for the evaporator.
5. The temperature of the air flow was recorded using the thermistor, recording 3 values across the top of the condenser’s area of flow and 3 values across the bottom of the condenser’s area of flow, a total of 6 recorded values. This was repeated for the evaporator.
Results and Discussion
Results and Discussion
More work done at top of evaporator and condenser
Conclusion
Fan speed and efficiency of system directly related
Heat loss throughout system
The heat absorption rate by the evaporator and the heat rejection rate by the condenser were not equivalent
Air Flow-rate affected condenser more than evaporator
Change in enthalpy of coolant not equal to change in enthalpy of air

Objectives
-Measure Power Requirements of the System
-Determine effect of air flow rate
-Calculate evaporator heat absorption rate and condenser heat rejection rate using air flow data
-Calculate evaporator heat absorption rate and condenser heat rejection rate using coolant data
-Calculate Coefficient of Performance and compare to ideal COP

Jesse Austin
Christopher Nartey
Sunny Patel
Meera Sharma
Equipment
Recommendations
Temperature-controlled environment
Take non-ideality into account
More readings of air velocity and temperature accuracy
Digital Gauges for properties
References
1. Refrigeration cycle
http://nstar.apogee.net/res/recrefr.asp
2. Vapour compression cycle
http://www.alephzero.co.uk/ref/vapcomcyc.htm
3. Felder, R. M. and Rousseau, R. W, Elementary Principles of Chemical Processes. 3rd Edition, John Wiley & Sons, Inc. 2000.
4. Smith, R.H., Van Ness, H.C. and Abbott, N.M., Introduction to Chemical Engineering Thermodynamics, 5th Ed., McGraw Hill, New York (1996).
5. Perry, R.H. and Green, D.W., Chemical Engineerís Handbook, 7th Ed., McGraw Hill, New York (1999)
Questions?
Significance of Results
Qair does not equal Qcoolant
Air flow rate is affected by change in system
Higher fan speed gives better operation

Poorly Insulated Pipes

Assuming Ideality in Calculations
Error Analysis
These show the inefficiency of the system
Results and Discussion
Heat of the condenser is different from heat of the evaporator
Schematic
Thanks for listening
Procedure
6. The four pressure gauges were recorded.
7. The four temperature gauges were recorded
8. The mass flow rate of the refrigerant was recorded.
9. Steps 1 through 8 were repeated for the other fan speed settings.
10. After finishing the collection of necessary data, the compressor was turned off, the system was turned off, and the equipment was returned to the proper locations.
Condenser
Evaporator
Compresser
Equipment
Refrigerant Mass Flow Rate Gauge
E. Provides readings for the mass flow rate of the refrigerant in the system.

Temperature Gauge
F&G. Various temperature and pressure gauges throughout the system in key positions.

Equipment
Fan Speed Operations
H. Two dials to adjust the fan speed of the condenser and evaporator.

The Wattmeter was important for determining the power usage of the compressor.

The Velocimeter (Below) and the Thermistor were important for determining the velocity and temperature of the air flowing from the condenser and evaporator.

Why do we need refrigeration?

What is Refrigeration?

Vapor – Compression Cycle

Practical evaporation and condensation pressures

High critical and low freezing temperatures

Low liquid and vapor densities

Low liquid heat capacity

High latent heat of vaporization

High vapor heat capacity


Refrigerant

Qair is not equal to Qcoolant at both stations
Theory
-1st and 2nd Law of Thermodynamics
-Isentropic Compressor
-Heat lost during condensation
-Heat absorbed by coolant during evaporation
-Constant temperature through expansion valve
-Carnot Cycle
P-H Diagram
Pertinent Equations
Energy Balance

Reduced Energy Balance
Enthalpy Equation

Enthalpy as function of heat capacity

Heat Capacity Equation

Mass flow rate of air

Density of air

Compressor power requirement

Coeffecient of Performance (Ideal)


Coeffecient of Performance (Actual)
Full transcript