What is System balance?

[RogGoetsch]

Gary
Traditional theories of learning that focus on knowledge reproduction (your method) rather than knowledge use, are inadequate when learning approaches advanced knowledge domains where tasks become more complex, dynamic, and ill-structured. . . . It is the stage of advanced knowledge acquisition that we discuss books like DOSSET.

When I began to manage technicians it came as a shock to me to discover just how rare good analytical skills are. Now I tend to separate techs into "how it works" types and "why it works that way" types. (I also encountered many "haven't a clue" types, but we kept them busy with installations.)

Dossat is great for the "why" guys if you can ever find one, but the "how" types need to be helped along in the beginning, and many will always need to be reminded to get the data and analyze the results before starting to change parts.

I think most posters to this forum are far beyond the basic skill levels addressed in cook-book approaches. That doesn't mean there is no place for such. Personally, I am grateful to anyone fighting to improve the skill level of our trade. God knows it needs it!

Actually, it takes great skill to reduce system analysis to an easily understood set of procedures. Just consider how difficult it is to extract the meaning of some of the more erudite posters to this forum! Understanding does not guarantee communication skills any more than intelligence is a reliable measure of emotional maturity.

Rog

[FreezerGeezer]

I agree. Gary's TECH Method isn't meant to teach you refrigeration, it's meant to instill in you (especially if you're new to the game - an apprentice or some such) a methodology for fault finding.
Many's the time in my younger days I would have found TECH method useful, instead of barging in like the proverbial bull in a china shop! ;-)

[Gary]

I agree. Gary's TECH Method isn't meant to teach you refrigeration, it's meant to instill in you (especially if you're new to the game - an apprentice or some such) a methodology for fault finding.
Many's the time in my younger days I would have found TECH method useful, instead of barging in like the proverbial bull in a china shop! ;-)

Actually, many old timers have found my methods useful. It is however more difficult for them as it requires un-learning and re-learning basic skills. It might be analogous to lifting your house and installing a stronger foundation, when the old foundation was strong enough to get by. The more experienced techs are often unwilling to go through the transition. Old habits die hard. Most techs throughout the industry are getting by, and have little interest in remedial training.

[Gary]

Actually, it takes great skill to reduce system analysis to an easily understood set of procedures. Just consider how difficult it is to extract the meaning of some of the more erudite posters to this forum! Understanding does not guarantee communication skills any more than intelligence is a reliable measure of emotional maturity.

It took me 4 years to do the research and write the books. That's 4 years, full time, without a paycheck. I know for a fact that there is no more efficient, more thorough, more accurate, more flexible trouble shooting sequence, having thoroughly tested every conceivable approach.

[Peter Croxall]

Hi Gary,
As an “Old timer” myself, I agree with you. After studying your books, it makes sense to think in terms of refrigerant temperature as apposed to pressure, (especially with the myriad of refrigerants we have to contend with now).

In my day one usually only had to contend with R22 and R12, although I did come across a few fridges running on Methyl chloride and SO2. Not very nice for the nasal passages.

[Brian]

Firstly I would like to pointout that there is no such conservation law that states "mass is conserved" and also the book is by the professor Dossat not Dosset. Cheers!!!!

[shogun7]

Sorry Brian, I didn't mean to confuse you.

[Gary]

Hi Gary,
As an “Old timer” myself, I agree with you. After studying your books, it makes sense to think in terms of refrigerant temperature as apposed to pressure, (especially with the myriad of refrigerants we have to contend with now).

Hi Peter,
The TECH Method was initially written before the new refrigerants were introduced. Even then it made more sense to think in terms of temps instead of pressures. With the new refrigerants, it was not necessary to revise the book. All my readers needed was a new P/T chart. The transition was relatively easy for them.

In my day one usually only had to contend with R22 and R12, although I did come across a few fridges running on Methyl chloride and SO2. Not very nice for the nasal passages.

Now there's an understatement. Anyone who thinks the introduction of *****s was a bad thing needs a snootful of the nasty stuff they replaced.

[Gary]

Pressures? Useless, I wish, like Gary says, they were never included on service guages.

Before the new refrigerants were introduced, I used to recommend that people paint over the pressure scales on their gauges, so they would be forced to look at the temperature scales. From a troubleshooting viewpoint, temps are what matters. It made their job MUCH easier.

[RogGoetsch]

I think I was lucky in that, from the beginning, evaporators and condensers were of course heat exchangers all abiding by the formula kW = AxUxdT or AxUxLMTD.

The heat exchange suface is the exposed surface of a material that has a coefficient of heat flow W/m².K meaning that U amount of Watts will pass per m² with a 1K (1°C) temperature difference.

Just a reminder that "U" is the overall coefficient of heat transfer, so the thermal conductivity of a given material is usually only a small factor in heat exchanger design. In my experience, surface film factor coefficients rule.

In one biomedical heat exchanger using stainless steel instead of copper for example, the thermal conductivity of copper was something like seven times that of stainless, but when U was calculated with film factors, the difference in U values between the two heat exchangers was too small a decimal to survive rounding.

The same is not true of insulating materials where surface convection coefficients are not very significant.

Rog

[shogun7]

[QUOTE=RogGoetsch]Just a reminder that "U" is the overall coefficient of heat transfer, so the thermal conductivity of a given material is usually only a small factor in heat exchanger design. In my experience, surface film factor coefficients rule.

Rog,
With regards to surface film factor coefficients ruling we know how oil logging has a significant impact on the operation of a remote, low-temperature refrigeration unit in addition, a similar situation exists when we have laminar oil flow which results in poor oil return to the compressor and poor heat transfer so a concept to remedy this situation is called Altered Bi-phase Flow (ABF) regime; an annular (ring-like) film maximizes heat transfer throughout the evaporator, increasing the useable evaporator tube surface area. The result is a cooler tube wall with a higher evaporator pressure. The technology’s primary benefits are the elimination of laminar refrigerant flow and the resulting poor heat transfer coefficients.
The present method has been focused on having liquid at the entry to the evaporator to ensure that the maximum heat transfer capacity was available. This new approach focuses more on the rate of heat transfer. The method has been described as “distributed enthalpy,” because the slow-moving refrigerant at the evaporator entry is more evenly distributed throughout the length of the evaporator. It develops a multistage pressure drop in that it separates the liquid from the vapor and entrains the liquid into the higher vapor velocity. The resulting temperature and pressure uniformity within the evaporator improves frost formation, refrigerant feed stability, compressor ratios, and net cooling rate. That directly impacts product temperature recovery and the annular flow that is derived from distributed enthalpy encourages oil to return to the crankcase and provides proper lubrication — even after extended periods of operation.

[shogun7]

Lol, so what about it, Shogun?

What about what? Merk
Is that supposed to be cute or do you have a question?

[RogGoetsch]

With regards to surface film factor coefficients ruling we know how oil logging has a significant impact on the operation of a remote, low-temperature refrigeration unit in addition, a similar situation exists when we have laminar oil flow which results in poor oil return to the compressor and poor heat transfer so a concept to remedy this situation is called Altered Bi-phase Flow (ABF) regime; an annular (ring-like) film maximizes heat transfer throughout the evaporator, increasing the useable evaporator tube surface area. The result is a cooler tube wall with a higher evaporator pressure. The technology’s primary benefits are the elimination of laminar refrigerant flow and the resulting poor heat transfer coefficients.
The present method has been focused on having liquid at the entry to the evaporator to ensure that the maximum heat transfer capacity was available. This new approach focuses more on the rate of heat transfer. The method has been described as “distributed enthalpy,” because the slow-moving refrigerant at the evaporator entry is more evenly distributed throughout the length of the evaporator. It develops a multistage pressure drop in that it separates the liquid from the vapor and entrains the liquid into the higher vapor velocity. The resulting temperature and pressure uniformity within the evaporator improves frost formation, refrigerant feed stability, compressor ratios, and net cooling rate. That directly impacts product temperature recovery and the annular flow that is derived from distributed enthalpy encourages oil to return to the crankcase and provides proper lubrication — even after extended periods of operation.

I think what Marc means, and with good reason, is that this is just a teaser. What about "ABF"? How is it achieved? What is the design difference? Any examples with data? What is your experience with it?

Your remarks serve as an introduction but seem to stop there without contributing anything of substance. At least please refer us to your sources.

Thanks,

Rog