Simple Simulation of Refrigerant Cycle

In this screencast I'm going to demonstrate how to use an interactive simulation that models an ordinary Vapor compression cycle using the refrigerant

In this screencast I'm going to demonstrate how to use an interactive simulation that models an ordinary Vapor compression cycle using the refrigerant R134a. Then a snapshot of the simulation where we show a pressure enthalpy diagram and indicate the direction of the process.

We have a compressor condenser and then a throttle, where we get Cooling, and then evaporator to get back to saturated Vapor. We can look at either pressure enthalpy diagram or temperature entropy diagram, and we can control the two pressures the condenser and evaporator pressure let's look at the simulation. 

So here's the simulation we can change the pressure. If we lower the pressure you'll notice the coefficient of performance is increasing. So the coefficient of performance is how much heat we removed and evaporator divided by how much work we put in since the objective is to remove heat if we lower this pressure.

We indeed increase the coefficient of performance but we're lowering the temperature where we get condensation. So since we have to exhaust heat to a lower temperature that means we have a smaller delta T say between the back of the refrigerator and the room air.

So we have much slower heat transfer which would mean larger area for heat transfer, so we can raise the evaporator pressure coefficients from forest becomes very large.

But now we've raised the temperature since as pressure goes up the saturation temperature goes up, so we now have much less cooling much less heat transfer and we have much higher temperature that we can't cool any more than. So even though coefficient the performance is higher it may not be good way to operate it for trying to cool something down. 

We can look at temperature entropy diagrams and as we said as we raise this this shows directly we raise this evaporator pressure we raise this temperature we raise the condenser pressure we raise this temperature.

The psych the actual cycle is here and if we move the mouse over it shows here we have saturated liquid we go through a throttle we get two phases this is where we get the cooling. And so the coefficient performance which is Cube cold temperature QC overwork is also related to the enthalpies that are shown here in the details. 

So this is a common cycle for refrigeration, and so understanding it's Behavior on a pressure enthalpy diagram is valuable for understanding best how this process takes place and how change of variables affects it.

• [accordion]
• 1. ANSI-ASHRAE Ventilation for Acceptable Indoor Air Quality
• 2. Method of Testing HVAC Air Ducts - ANSI
• 3. Indoor Air Quality Guide Best Practices for Design Construction and Commissioning
• 4. 2018 ASHRAE Handbook Refrigeration
• 5. Fundamentals of HVAC Control Systems
• 6. ASHRAE Green Guide The Design Construction and Operation of Sustainable Buildings