practical benifits off using a ph chart ?

[knight rider]

hello to everyone,

can some one please inlightern me on the PRACTICAL benifits off using a ph curve chart
when i have plotted all the details onto the chart eg , pressures, tempertures , superheat and subcool ects , and i am look at the chart,what am i looking for ?
will this show my what duty the machine is doing in kw

MANY THANKS

[Peter_1]

Most charts are in kJ, so you have to convert it.
You mostly don't need in real life but if your don't understand this cahrt not completely, the many times you will make errors in real life.

[US Iceman]

Let's say you plotted the superheat and subcooling from a specific system. When you do this you might see the location for the subcooling might not be subcooling at all. Pressures and temperature from a PT table only tell you so much. By plotting the data out on PH diagram you actually see what the condition of the refrigerant is.

I use these a lot to show people what is happening in the system.

The diagrams will not give you kW (or Tons) of refrigeration because you do not know the mass flow. But they do show the effect of the gas volume increase if the suction superheat is too high.

You just need to get comfortable using these.

[Andy P]

Two advantages for you:

If you measure the compressor kW input (and make due allowance for oil cooling) you can work out the mass flow and hence cooling capacity and CoP.

The chart saves you having to wade through shedloads of superheat charts to achieve the same result:D

Any system complexity (2-stage, economiser etc) make it all a bit more complicated

cheers

Andy P

[taz24]

Ph charts are a snapshot for the second you plot the information. They are good for translating practical evidence to the theoretical.
You can design to size of a system before you build it or if you have a working system you can see what is hapening within the system.
Iv'e been in fridge a few years now and I have never used a Ph chart in anger but they are usefull for training and theoretical design.

taz

[750 Valve]

Magical tool! Uses are endless. Highlights how good a friend mr subcooling is to us fridgies, its also the easiest way for confirming non condensables via discharge temp.

[Peter_1]

Iv'e been in fridge a few years now and I have never used a Ph chart in anger but they are usefull for training and theoretical design.
taz

I think you fully understand the basics and that's why you rarely need it once you understand what you're doing when working on fridges.

I think you don't realise any longer but it is because you once learned and understood all these that this is the reason why you understand it now and why you perhaps find that some questions seems so basic, so stupid.
It all seems then so simple.

Once you see through the whole PH chart, you don't need it that much any longer. That's true.

I read today in a popular Dutch magazine (Quest) an article where they describe how a fridge work. They explained that the compressor compress the gass and that this liquid :confused: is re-entered in the system again to complete the whole cycle. They never mentioned a condensor.

[taz24]

I think you fully understand the basics and that's why you rarely need it once you understand what you're doing when working on fridges.


I would like to think I understand the basics (although I have seriously wondered somtimes:D ).

I was never a theoretical person. I was always hands on, I learnt by working on things and watching, talking to, listening to better engineers than I could ever hope to be.
I did not know realy how to use the Molier charts until about 6 years ago. I now wish I spent more time trying to learn the theoretical as well as the practical.
My out look on life is if you have learnt somthing today then it can't all be bad.:)

I like learning now, I used to hide from it before but after all these years in the trade I can honestly say that engineers need to be very open in there way of thinking. If we become fixed and unflexible then in my opinion your beter off looking to somthing else because the passion for the trade would be gone.

My views only and they may not be right. I will be the first to accept I may be wrong and hopfully that makes me flexable to new challenges.

taz.

[US Iceman]

I was always hands on, I learnt by working on things and watching, talking to, listening to better engineers than I could ever hope to be.


That is how I started too. I used to get all sorts of calls from other contractors to help them solve strange problems. Sometimes the wholesaler would send strange jobs to me.

I begin to realize there was more to this business than what I had been previously exposed to. This led me to quickly develop an active interest in learning anything I could about refrigeration.

Mollier diagrams was one of the first topics I went after.;)

[taz24]

Mollier diagrams was one of the first topics I went after.;)

Many, many moons ago I was working for a large industrial animal by product company. They had lots and lots of large industrial machinery. There was a requiring problem with a cold storage room and in the end a consultant was called in.
I got to know him well while he was there and in the week he was there I watched him measure, calculate, probe, adjust he just about tested and calculated the system from new. I was mesmerised he calculated the problem and it was then solved.
I learnt then that there was more to fridges than just fitting a set of gauges.


taz.

[US Iceman]

I learnt then that there was more to fridges than just fitting a set of gauges.


Add don't forget the mandatory drum of refrigerant that goes with the gauges. If all else fails, fill it it!:(

[taz24]

Add don't forget the mandatory drum of refrigerant that goes with the gauges. If all else fails, fill it it!:(


Now your talking my type of repair:p


:D

taz

[The Viking]

Many, many moons ago I was working for a large industrial animal by product company.

McDonald's or Burgerking?
:rolleyes:

[taz24]

McDonald's or Burgerking?
:rolleyes:

I sometimes wondered:D

taz

[SteinarN]

I only use a p-h chart once in a while. But i rely heavily on the understanding of the fundamentals behind the chart on nearly every fault finding job. The first thing i learnt when i started studying refrigeration was damp air chart. Then i went on with the p-h chart. I feel i have a good grip on the fundamentals behind the chart. I feel this understanding is very important in order to fully (hopefully) understand the refrigeration process, to be able to diagnose a system and to find out whats inside the different pipes in a refrigeration system and whats happening inside.

[weatherman]

A ph chart is also called a Mollier diagram. It can be used to calculate the system COP and show glide and slide on some refrigerants. They can be in BTU per lb or KJ/KG of refrigerant flow, they can also show you the theoretical motor input power. In the UK as part of a city and guilds examination, you are required to show that you can use these charts and identify information from them