Introduction to Food Engineering

Home Syllabus
Material Balances Energy Balances
Fluids Laminar and Turbulent Flow Volumetric Flow and Friction Bernoulli's Equation and Pump Power Flow Measurement
Thermodynamic Properties
Modes of heat transfer Conduction in walls Conduction in multilayered walls Convection heat transfer Forced Convection Free Convection Overall Heat Transfer Coefficient Heat Exchangers Unsteady State Heat Transfer Heisler Charts
Decimal Reduction Time F value General Method Improved General Method
Properties of Air and Water Vapor Psychrometric Chart
Moisture Content and Drying Rates Drying Time
Single Effect Evaporator Multiple Effect and Industrial Evaporators
Refrigerants Vapor Compression Refrigeration System Ideal and Non-Ideal Cycle
Ice Crystallization Freezing Time Freezer Selection
Instructions List of Experiments

Ideal and Non-Ideal Refrigeration Cycles 

Learning Outcomes

At the end of this module, you will be able to:

  1. draw a refrigeration cycle on a PH chart for a system operating under ideal conditions
  2. draw a refrigeration cycle on a PH chart for a system operating under non-ideal conditions
  3. obtain enthalpy values of a refrigerant as it flows through different locations within the refrigeration system

Content

In the previous module, you learned various mathematical expressions that help design a vapor compression refrigeration system. Typical design questions to accomplish a certain amount of cooling include calculating the flow rate of the refrigerant, the size of the compressor, heat absorbed by the evaporator, and heat discharged at the condenser. Similarly, we evaluate the performance of an existing refrigeration system by calculating the coefficient of performance. In an industrial environment, the refrigeration systems may operate under ideal conditions, or most often, under non-ideal conditions. In this module, we will consider both these conditions. In the next video, you will learn how to draw a refrigeration cycle for a system that is operating under ideal conditions to obtain enthalpy values required for design calculations.

In the next video, we will work through a numerical example of obtaining enthalpy values from a PH chart for a system operating under ideal conditions.

As we observed in the above video, under ideal conditions, the refrigerant enters the compressor as a saturated vapor, and it enters the expansion valve as a saturated liquid. However, many industrial systems operate under non-ideal conditions, where the refrigerant enters the compressor as superheated vapor, and it enters the expansion valve as a sub-cooled liquid. These non-ideal conditions shift the cycle locations on the PH chart. In the next video, you will learn how to account for the non-ideal conditions.

The next video is about another numerical example on how to obtain enthalpy values from a PH chart when the refrigeration system is operating under non-ideal conditions.

Recap

In this module, we observed how to draw a refrigeration cycle on the PH chart when the refrigeration system is operating under ideal or non-ideal conditions. Using the procedures learned in this and previous modules, you can obtain the enthalpy values from the charts and use them in the mathematical expressions for designing or evaluating the performance of a vapor compression refrigeration system.