Pressure Enthalpy Without Tears w/ Eugene Silberstein
RACT manual co-author Eugene Silberstein joins Bryan to talk about the titular topic of his book, “Pressure Enthalpy Without Tears.”
“Pressure Enthalpy Without Tears” is a book that introduces engineering concepts to HVAC technicians in a way they can understand and apply in the field. Enthalpy is a fancy way of saying “heat,” and we use it to refer to the total heat content (BTUs).
The pressure-enthalpy chart shows the relationship between the refrigerant pressure and enthalpy in a system; it’s like a P-T chart that shows the relationship between heat content instead of temperature.
Each refrigerant has its own pressure-enthalpy chart, but the points and lines on the chart usually form a right trapezoid. Dirty air filters and other less-than-ideal conditions can distort the trapezoid or shift it on the chart. Each side of the trapezoid represents the refrigerant inside a major component of the HVAC system: evaporator, compressor, condenser, and metering device. The pressure-enthalpy diagram allows you to get a look at individual components while keeping the entire system in mind.
To plot points on a pressure-enthalpy chart, you need the high side pressure, low side pressure, condenser outlet temperature, evaporator outlet temperature, and compressor inlet temperature. Pressure is usually measured in absolute units (rather than gauge units), but ballpark estimates are typically sufficient.
Entropy is another concept we need to consider. Compression theoretically leaves no additional entropy and is reversible. Crossing a line of entropy means that a process is no longer reversible.
Eugene and Bryan also discuss:
Technicians vs. engineers
Temperature vs. heat content
Psychrometric and pressure-enthalpy charts
Using the pressure-enthalpy diagram to assess operation costs
Electrical measurements
Predicting compressor failure
Putting passion into learning and trades education
You can visit www.escogroup.org/ to purchase “Pressure Enthalpy Without Tears” and access all of ESCO Group’s resources. You can also use the code HVACSchool22 for a discount on ESCO Group’s eLearning services.
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/.
Пікірлер: 44
Best in the business.
Best HVAC professor ever. Prof. Silberstein made theory very easy and made class enjoyable. I was lucky to spend 2 1/2 years with him.
5 minutes in and I already know this is going to be good content and Eugene sold another book.
Great video Bryan, Thank you for bringing all this out to the trade. Thanks again.
Best professor ever!!! #SCC. You are the man Gene!
thank you. I ordered the book today on Amazon.
I ordered the book....Can't wait to get it...You should create a field app.
Could u please discuss it again using PV, TS & pressure enthalpy diagrams placed in 3 different columns and psychrometric charts And actually show how u used them to predicted compressor failure or some other impending failures or incidents. Also, when u mention variables like enthalpy, entropy, pressure, temperature, density please always mention if it is for ambience or the refrigerant. Thank u
It would be interesting to see a sensitivity analysis of values that would result in resolution power of this system method. If modeling changes are possible then different compression technologies could potentially evaluated for performance.
Might be a fun topic to talk about: heat mode. There are just a crazy amount of techs that dont understand heat mode properly and how important gas temperature is and how important insulation of the hot line is and how distance can severely affect efficiency due to the temperature drop/loss over longer runs like above 30ish ft.
@marconantel7735
Жыл бұрын
I agree! Cause I’m one of them!
What is the difference between thermal efficiency and coefficient of performance?
When a turbo -expander is used in place of a expansion valve, it's then closer to a right trapezoid. The adiabatic expansion is closer to isentropic expansion.
Ashworth college pressure empathy charts were the first things we had to learn.1 year later me not no shite about p.e charts lol.The square represents the metering device,the compressor,the evaporator and the condenser.
Is this excel spreadsheet available?
Line ( dome line) represents saturated liquid or saturated vapor? and everything within the dome is also saturated liquid or saturated vapor? And Left & right of the dome is sub cooled liquid and super heated vapor respectively? Please verify? Thank u
This is fascinating
Kids solve those Rubic cubes without even looking at the cube.
People say you must make sure the refrigerant is fully vapor before entering the compressor or else it will damage the compressor. But I cannot find any video about how to determine the state of the refrigerant. 😢
Can you talk about oil trap?
I know this is a little off topic however, if you have a heat pump condenser with an orfice and an evaporator with a TXV will the system work at all, or bad idea? thank you for your response.
@robertvanalst7955
2 жыл бұрын
What did you just say
@SupremeRuleroftheWorld
2 жыл бұрын
that setup does not make sense.
@billmabrey3828
2 жыл бұрын
You are referring to a heat pump system. Correct? Yes it can work. He is referring to having a fixed orifice metering for heating mode and txv for cooling. * By the way. In heat pumps the coils are referred to as indoor and outdoor. Because, they change(condenser/evaporator) from indoor to outdoor depending on which mode(heating or cooling) the equipment is operating in.
@SupremeRuleroftheWorld
2 жыл бұрын
@@billmabrey3828 a orifice would be extremely bad for efficiency and severly limits its operational range.
@billmabrey3828
2 жыл бұрын
Are you telling me you've never come across residential equipment designed this way? It is somewhat a common design depending on what part of the country the system is designed to operate in
Question: Eugene mentioned that you could actually take enough measurements only at the compressor/condenser unit and that would be sufficient to do the analysis. However, he says that you need to know the evaporator outlet temperature. To me, and to be accurate, it would seem that you would have to actually go to the actual evaporator and measure its outlet temperature right there? So I don’t understand how you can do all of this at the compressor/condenser unit outside.
@YouTubeCommunists
Жыл бұрын
Well the low side suction goes outside to the compressor ,there's your evap measurements.
@SpinStar1956
Жыл бұрын
@@KZreadCommunists So, even if the line traverses an area whereby it could pick up heat, due the whole suction-side being at a uniform pressure, you can then say (based on the refrigerant-type) that the evaporator must be the PT temperature? Thanks Jason for your reply! 😃
@YouTubeCommunists
Жыл бұрын
@@SpinStar1956 I will defer your question to someone more advanced than me,good luck!
@tom24057
8 ай бұрын
@@SpinStar1956 measuring the suction outside would be ok imo. You’d be getting true suction superheat (inc line set heat gains)
Yeah PE charts are cool and all but this guy is rocking Cornrows… and that’s really cool
Nice sir, regards from india
I have An early copy of PEWOT in blue binding from SCCC Brentwood, 2008
Just think......Willis Carrier understood all this 100 years ago. I don't claim to fully understand psychometrics, general understanding...yes.....on these guys level....no way. Stuff still baffles me.
@SupremeRuleroftheWorld
2 жыл бұрын
he understood the principle, not the intracacies.
The compression process in the refrigeration cycle is NOT reversible. (Not isentropic.) The isentropic efficiency of residential compressors runs between 70 to 80%. To have a reversible isentropic process would violate the 2nd Law. You find out the isentropic compression efficiency from the manufacturer. Then you plot your compression line leaning towards the right to a higher temperature than where the isentropic line intersects. But it is all good stuff for the tech to pick up. 😀 Following the isentropic line doesn't hurt anything - just makes that frenchy Sadi Carnot choke in his grave.
hi pressure enthalpy chart is proof that 150psi is far better for evaporator performance than 220psi [when I talk psi I mean temperature ] in the R134a automotive . A second condenser is often needed . The lower the psi the lower the temp but also the higher the % of liquid by 10--20% if u read the chart correct .[ flash gas ] Real world is I can get R134a at 150--160psi , Any engine Rpm on a 110---120f day . Vent temp 42-47 f [thermostat setting ] and low temp operates cycles 22--35 psi . Sight glass installed 100% full. I regularly achieve this with mobile plant / machinery being all other parts are working properly ie cabin insulation , tinted glass correct evap size .
Holy smokes.
I understand this guy is very smart but I'm having a hard time taking him seriously with the corn rows.
He may be a good author, but he is not a dynamic speaker. Falling sleep is easy with this speaker. Pod casts may not be his best method. Maybe straight lecture at a whiteboard is more helpful , where he can organize his thoughts better . Podcasts inherently allow one jump around a lot easier to jump off the Rails ! Good luck.