The Basic Refrigeration Circuit, Pressure & Enthalpy w/ Carter Stanfield
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- Опубликовано: 4 июн 2024
- (Audio Only) In this episode of the HVAC School podcast, Carter Stanfield, a co-author of Fundamentals of HVACR, talks about the entire refrigeration circuit. He also explains how to read and plot a pressure-enthalpy diagram.
The refrigeration circuit has four main components: evaporator, compressor, condenser, and metering device. When teaching, Carter likes to explain that boiling is a cooling process and condensation is a heating process. He describes saturation as the breaking point at which liquid refrigerant can no longer hold more heat (in the evaporator). The superheated vapor from the suction line then enters the compressor; the compressor adds even more superheat. So, the discharge line has very superheated vapor. In the condenser, saturation occurs when the vapor cools to the point that it can no longer hold more moisture; the temperature stays the same until the refrigerant becomes entirely liquid. Subcooled liquid travels to the metering device via the liquid line. The metering device reduces the pressure of the refrigerant and feeds the evaporator. However, some flash gas occurs and helps drop the temperature of the remaining liquid.
A pressure-enthalpy diagram illustrates the refrigerant's changes in and out of the saturated state as it moves through the refrigeration circuit. The chart looks like a curved dome, and saturated states are inside the dome. Pressure is on the y-axis, and enthalpy is on the x-axis. Pressure is a logarithmic arrangement; a linear arrangement would be impossible to plot. The bottom of the chart shows low pressures, and the top shows high ones. Enthalpy is the heat content of the refrigerant. We express it in BTUs/lb.
When you plot one of these diagrams, you can start with four lines and readings: high and low-side pressure, suction line temperature into the compressor, and liquid line temperature into the metering device. You will end up drawing a parallelogram shape on the chart.
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Great information. Thank you HVAC School.
Thanks. Good listening
Love what you have going here🎉
Love the intro music
This is a great tool for both experienced and from my perspective, somewhat new people. But I do have a question, anyone know the title of the jazz at the beginning? Thanks
Man y’all guy rock!! It’s good you all do this even for refreshers that people have forgotten about it over the years!! Thank y’all!! I’ll be listening to the pod casts.. never listen to pod cast but y’all guys make it interesting!!!
I appreciate all you do for education God bless!
Lmao that’s funny as shit beer can cold that’s what I called it when I first started
Great information & Thank You to you both.
one of the guys I work with had an AC unit with a weird symptoms. This is about a 4 ton American Standard 460 VAC AC PKG RTU. R22, 12 years old. Not cooling the space. Suction line is warm, like 84F, ambient is 90F, room temp is 75F, pressures are about 92/280PSIG. Superheat is very high sub cooling is in the over 20, LLT is about 82 -ish. He said the return air temp is about 80.... He recovered the charge and weighed it in. The compressor amp draw is 3.8a with an RLA of 5.9. Im thinking the compressor is weak with that amp draw and such a warm suction line. He tried to slow down the blower (belt driver ) It didn't seem to make much difference he said. Any ideas that stand out to you? Oh, its a scroll... it seems to me to be starved and that high back pressure and not that high of a load. Unless he gave me inaccurate data.
Mike
Have you ever seen any cascade systems or ultra low refrigeration systems? Scientific equipment?
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