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Thread: Refrigeration 101
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29-11-2009, 10:06 PM #101
Re: Refrigeration 101
Last edited by Gary; 29-11-2009 at 10:08 PM.
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30-11-2009, 07:22 AM #102
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30-12-2009, 07:14 PM #103
Re: Refrigeration 101
yes! I have one of Gary's TECH books and they cut to the chase to real t/s, a great purchase if u can!!!
just a pup on the porch:)
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08-01-2010, 02:33 AM #104
Re: Refrigeration 101
Respected Gary
Where I can get the books Tecch method troble shooting? Is there any agent in India?
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08-01-2010, 02:53 AM #105
Re: Refrigeration 101
Last edited by Gary; 02-02-2011 at 01:54 AM.
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25-01-2010, 03:07 PM #106
Re: Refrigeration 101
This thread is a wealth of good information. It is a shame that the people who need this info the most do not look at / subscribe to free sources of education such as this web site.
Thanks
From the west side of the pond.
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16-02-2010, 08:04 AM #107
Re: Refrigeration 101
Hi, I have a quick question about connecting gauges, don't think it has been asked before. I always seem to release alot of gas when connecting guages to split A/C systems. Is there a nack to it, like pumping down a system before hand. Is it best to connect when the system is running or off, both high and low sides.
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17-02-2010, 06:11 AM #108
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Re: Refrigeration 101
Turn unit on cooling, close partially valve on smaller pipe and when pressure falls to around 1 bar disconnect your gauge. Open valve fully and put valve caps.
Or buy Refco Quick Couplers.Last edited by nike123; 17-02-2010 at 06:20 AM.
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17-02-2010, 10:17 AM #109
Re: Refrigeration 101
Hi gary sir
Before 25 years ago self diagnosing systems are in market!! Ex: carrier 30 GT chiller. Now all commercial chiller manufactures are designing self diagnosing based refrigeration fundamentals. Some sample alarms such as- low suction super heat, high saturation suction temperature, low discharge superheat…………….etc.
Your 101 is very useful, thanks a lot
Moideen-dubai
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28-02-2010, 06:21 AM #110
Re: Refrigeration 101
Something like e.g. - low suction superheat - is a symptom, not a diagnosis. In my opinion, these systems are not self-diagnostic.
When they can say things like - insufficient evap airflow, or liquid restriction, or refrigerant overcharge, or inefficient compressor, etc, etc. etc... then I will be impressed.Last edited by Gary; 28-02-2010 at 06:25 AM.
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01-03-2010, 03:54 PM #111
Re: Refrigeration 101
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03-03-2010, 02:26 AM #112
Re: Refrigeration 101
Gary,you're a legend.I always follow your post since i become a member and your ideas are great.
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03-03-2010, 02:44 AM #113
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03-03-2010, 03:02 AM #114
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Re: Refrigeration 101
Something like this:
http://www.ecotechnics.it/en/product...lock-2000.html
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03-03-2010, 05:04 AM #115
Re: Refrigeration 101
Yep... something like that.
I had a couple diagnostic programs that I marketed on floppy disks back in the early 1990's. One for refrigeration and the other for A/C.
Crude but effective. Programmers would have a good laugh, but it told you what was wrong with the system.
Then they started putting USB connectors on printers and the printer function no longer worked. Started getting complaints that my programs wouldn't print the results, so I discontinued the products. I'm a service tech, not a programmer.Last edited by Gary; 21-03-2010 at 06:41 AM.
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22-03-2010, 01:54 PM #116
Re: Refrigeration 101
i thnk a cooling effect on d finger will appear...due to d reason- d water on d finger will absorb latent heat of vapourization nd will vapourize...as a result d temp. of d finger will fall nd a cooling effect will b produced...
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31-03-2010, 07:41 PM #117
Re: Refrigeration 101
good explanation welldone
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13-04-2010, 08:29 PM #118
Re: Refrigeration 101
hi guys this is a great idea love it i will have to read the technical stuff again cos some of it leaked out my head already an i have learned some things as well an only been in game 20 plus yrs if i may be so bold as to make a small contribution even though most of you are super technical more than me not enough engineers stop and actually look at what there working on an do the stuff i was taught look at it listen to it and feel it there the most important tools we have you can see a design floor in a system and adjust for it you can hear a compressor straining under excessive load and you can feel if an evap is fully wet all the way accross and then ya can break out the super tools to fix it
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25-04-2010, 05:56 PM #119
Re: Refrigeration 101
There seems to be a great deal of confusion about subcooling, so let's take a closer look:
The vapor loses its heat and turns to liquid as it moves very rapidly though the condenser. This does not happen all at once, it is a gradual process.
There is a point where the last vapor bubbles disappear and the mixture becomes solid liquid. Let's call this the "solid liquid point" or SLP.
Technically, if there is enough refrigerant to modulate the superheat at the evap outlet, then the system will function properly, but this is not the full story. Vapor bubbles travelling through the TXV orifice over a long period of time will wear out and distort the orifice, so to ensure long life for the TXV we want solid liquid at its inlet.
So... our minimum charge would have the SLP at the TXV inlet.
At the other extreme, we do not want liquid backing up into the condenser as this takes up condensing space and drives up the high side pressure.
So... our maximum charge would have the SLP at the condenser outlet.
The problem with the minimum charge is that changing conditions could have vapor bubbles at the TXV inlet. The problem with the maximum charge is that changing conditions could have liquid backing up into the condenser.
So... the ideal charge would have the SLP somewhere in between the TXV inlet and the condenser outlet. Thus, we want the SLP to be at the receiver outlet... which is why the sightglass is normally placed there, and why we want to measure subcooling there.
If we monitor the subcooling while observing the sightglass, on a wide variety of systems, we will find that the last vapor bubbles disappear at about 10-15F/5.5-8.5K subcooling. Thus we can identify the SLP by measuring the subcooling at the receiver outlet, ensuring that (with all else functioning properly) we are neither undercharged, nor overcharged.
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26-04-2010, 02:14 PM #120
Re: Refrigeration 101
Respected Gary,
Thank you very much for your "Refrigeration 101", the highly informative article.
May I ask you how can we check the heat absorbing capacity of a fin and tube evaporator, if we do not have any product details on it? Just we have the physical size of tube diameter, distance between end fins, fin spacing, fin thickness, number of tubes, number of elbows, fin width, refrigerant temperature, and cabinet temperaure. Also we know the fin and tube material, refrigerant and its properties. (forget about the oil film on the inner wall of the tube).
Wishing you all the very best
Thank you
Rayin
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28-04-2010, 11:39 PM #121
Re: Refrigeration 101
Gary that all sounds good there are actually 2 kinds of superheat evaporator and suction vapor since you failed to mention that. But lets do some
transmission heat load calculations:
If a wall has a u factor of .114 area of 90 square feet with a inside temp of 80 degrees what would the heat transmission be gary? In btu/hr
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29-04-2010, 02:08 AM #122
Re: Refrigeration 101
There is only one kind of superheat... but lots of different places to measure it.
Heat load calculations are outside the scope of this thread.
If you would like to start a thread about heat load calculations... go for it.Last edited by Gary; 29-04-2010 at 03:52 AM.
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17-05-2010, 10:12 AM #123
Re: Refrigeration 101
I didn't think starting a new thread for my mind blank was a great idea, and this was the closest thread i could relate my thread too.
I am new into the refrigeration industry and I can't remember what a capillary system is.
I have done a small search on google and have not made sense of the results. I was wondering if some one could explain a simple capillary system. Thanks...
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17-05-2010, 08:14 PM #124
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Re: Refrigeration 101
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18-05-2010, 08:47 PM #125
Re: Refrigeration 101
capillary...
Somewhere in the coil the flow of refrigerant is slower and also the pressure drops over the distance it has to traval? right?
so does it travel this distance loosing pressure in a small coil pipe in hopes when the refrigerent gets to the evap (larger pipe coil) its lost enough enough pressure to have a zillion vapour droplets colleting heat? like a thermal expansion valve, but with out the sensor or valve?
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19-05-2010, 02:07 AM #126
Re: Refrigeration 101
great job gary, i liked what i read.
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24-05-2010, 06:57 AM #127
Re: Refrigeration 101
Gary,
When you say "Generally speaking, a freezer should have 6-8F/3.5-4.5K superheat, a cooler should have 8-10F/4.5-5.5K superheat, and an A/C should have 12-16F/6.5-9K superheat."
At what abient temp are we talking here?
75 degree's?
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25-05-2010, 06:05 AM #128
Re: Refrigeration 101
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27-05-2010, 07:30 PM #129
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28-05-2010, 01:29 AM #130
Re: Refrigeration 101
How does SLP concept this relate to the concept of 'liquid cooling'?
Where : LC = Tc,sat - Txv,in
A few points to note:
1. LC will vary as Tc,sat varies over the cycle range;
2. The allowable subcooling (SC = Tc,sat - Tc,exit) differs for different condenser types. SC of 5.5-8.5K will be a problem for plate condensers (2-4K), & air-cooled condensers (~ 0K).
3. In the quest for increased SC, be careful of not pushing up Tc,sat. Basically, Tc,sat levers up off the cooling medium temperature. There is a happy balance point for each system.Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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28-05-2010, 06:56 AM #131
Re: Refrigeration 101
In my heat-pump trials, I have observed an influence on evaporator SH, due to ambient air temperature movements.
If Ta,in falls during the range of test, SH will roll down a little more than if Ta,in is constant.
If Ta,in rises during the range of test, SH can often end up being almost constant over the test duration.
The influence can be in the range of ~ 1-3K, depending on the operating SH of the machine.Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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28-05-2010, 08:07 AM #132
Re: Refrigeration 101
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28-05-2010, 08:19 AM #133
Re: Refrigeration 101
There is no doubt an ideal balance for each specific system... and I would not recommend SLP at the condenser exit for any system.
What I have found works reasonably well for refrigeration systems in general is to have the SLP in between the condenser outlet and the TXV inlet.
Generally, I would want the SLP to be near the receiver outlet and this is where I measure the SC. I suspect this is the very reason sightglasses are usually mounted near the receiver outlet.
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28-05-2010, 08:22 AM #134
Re: Refrigeration 101
Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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28-05-2010, 08:31 AM #135
Re: Refrigeration 101
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28-05-2010, 09:21 AM #136
Re: Refrigeration 101
Originally Posted by desA
How does SLP concept this relate to the concept of 'liquid cooling'?
Where : LC = Tc,sat - Txv,in
A few points to note:
1. LC will vary as Tc,sat varies over the cycle range;
2. The allowable subcooling (SC = Tc,sat - Tc,exit) differs for different condenser types. SC of 5.5-8.5K will be a problem for plate condensers (2-4K), & air-cooled condensers (~ 0K).
3. In the quest for increased SC, be careful of not pushing up Tc,sat. Basically, Tc,sat levers up off the cooling medium temperature. There is a happy balance point for each system.
There is no doubt an ideal balance for each specific system... and I would not recommend SLP at the condenser exit for any system.
What I have found works reasonably well for refrigeration systems in general is to have the SLP in between the condenser outlet and the TXV inlet.
Generally, I would want the SLP to be near the receiver outlet and this is where I measure the SC. I suspect this is the very reason sightglasses are usually mounted near the receiver outlet.
Sub-cooled boiling & gas evolution in direct liquid lines are part & parcel of a liquid line's behaviour (R-134a). This may be different for a receiver-based system.
The limiting system mass charge will be the one at which the Tc,sat value either jumps by 1-2K (non-linear jump), or where Tc,sat begins to climb rapidly. At this same instant, the pressure drop on the low-side reduces rapidly. These effects can be observed during refrigerant charge-determination trials. This seems to be a switch-over point from an evaporator-dominated system, to a condenser-dominated system.
I'd say that basic rules-of-thumb are useful for field applications, but, for new designs, the system characteristics for each case, will need to be carefully evaluated.Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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28-05-2010, 02:11 PM #137
Re: Refrigeration 101
This will very much depend on the magnitude of the TD itself.
For instance:
TD=10K ; SH = 0.5*10=5K; SH = 0.7*10=7K
TD=20K ; SH = 0.5*20=10K; SH = 0.7*20=14K
TD=30K ; SH = 0.5*30=15K; SH = 0.7*30=21K !!!
That's asking for a fair-sized SH. In all likelihood, you'd have a tremendously high Tc,discharge temperature.
The Magoo rule seems to be applicable in low TD applications & may need to be adjusted for high TD applications.
Like everything in the rhvac game, some level of sound engineering judgement will need to be made in each specific application.Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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29-05-2010, 12:18 AM #138
Re: Refrigeration 101
Gary...
may I first thank you for posting this "refresher" and secondly thank you for continuing your input to the Refrigeration world after your "semi-retirement".
I'm no fridgey...but at 33 and experienced it for 8 years, no quals gained, your "basics" brought it all back and has really urged me to follow the trade.
I'm an automation eng by trade, I experienced 8 years as a services eng with ammonia gas in a food factory, working with Frick and Grasso screws in pumped overfeed systems to blast & spiral freezers plus -26c cold-storeage. Looking back I loved it! It was like a black art: food at 60+ degrees going into a box and coming out frozen!!! A magic box that I knew the code of; well I assumed I did. I was working in a role that I wasn't qualified for, had no proper experience of yet getting by... really dangerous looking back. Stupid or getting by? Stupid I'd say, but someone was assessing my skills and passing me capable!
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29-05-2010, 01:08 PM #139
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31-05-2010, 11:19 AM #140
Re: Refrigeration 101
With regards to this thread which I think has been very interesting t read, I am extremley new to this forum and to refrigeration all together. You seem to mention a lot about different heat loads, can someone please explain to me what a heat load is and how it would effect the refrigeration system?
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06-07-2010, 02:17 AM #141
Re: Refrigeration 101
I am in school for HVACR, I will be graduating in Oct. I have used this site many times for research, and I am pleased with all of the info. I am struggling with the wiring diagrams (showing sequence of operation), any link you may have on basic wiring would be extremely helpful Thank You for your time Russell Peters (Cool Tool)
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02-08-2010, 12:34 PM #142
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28-08-2010, 02:39 AM #143
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21-09-2010, 11:07 PM #144
Re: Refrigeration 101
i would like to ask one question sir i have one refrigeration compressor make sabroe modl tsmc 108s using refrigerand 22 now adays it have loding problam it dosend get safishnt pumbing, then i open the compressor icant find eny mager problums but its oil pressur getting 4.5bar
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22-09-2010, 06:23 PM #145
Re: Refrigeration 101
Hi Gary
Good post,i could do with you in my tool bag so i can just pull you out and help me when im on site,im new to fridge game and im working on dryers mainly atlas copcos but it proving hard to get my head round and sort problems, cheers
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04-10-2010, 04:01 PM #146
Re: Refrigeration 101
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04-10-2010, 09:56 PM #147
Re: Refrigeration 101
Refrigeration System
1/Refrigeration system overview
*Propane Chiller: 57% Level
*LPG OH Condenser: 80% Level, LPG T°: -36°C
*Propane Economizer: 40% Level, PCV: 6 Bar, T° Gas: 9.5°C
*02Propane Compressor:
-PRO “A” -PRO”B”
.Capacity Control:
Set point (Bar) O.5 0.5
PID Out: 100% 100%
.High Stage Capacity Control:
Set point: 3.5 3.5 Bar
PID Out: 100% 100%
.Moy Amperes (Amp) 60.2 58.5
.Suction Pressure (Bar): 0.82 O.91
.Suction Temp (°C) : -41.3 -41.2
.Suction SH (°C): 5.0 3.3
.Intermediate Pressure (Bar): 4.0 4.4
.Intermediate Temp (°C) : 50.8 49.2
.Intermediate SH (°C): 55.5 51.6
.Discharge Pressure (BAR) : 13.5 13.8
.Discharge Temp (°C) : 74.0 72.1
.Discharge SH (°C) : 34.7 31.8
→Bypass Propane Condenser used in manual 0%
*Propane surge drum:
.Pressure: 14.5 Bar
.Level: 52%
*Gas Propane Exchanger:
.Propane T°: 34.75°C
.Gas T°: 29.25 °C
2/ Refrigeration Skid:
*Inlet Cold Separator: 26.4c°C
*Outlet Cold Separator: -28 °C
*Level Cold Separator: 40%
*Set point TCV: -45 °C (Bypass Cold Separator)
*Gas / Liquid Exchanger :
. Gas T°: 36.75 °C
.LPG T° : 8.85 °C
*Gas / Gas Cooler :
.Gas T° to sweet / sales gas Exchanger : 4 °c
.Gas T° to propane chiller: -16 °C
→*we can’t attend the cold Temperature -45°C
*Same times we have carryover of liquid on Propane Receiver
Please help me to identify the problem and correct them.Last edited by frank; 30-01-2011 at 01:49 PM.
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06-10-2010, 04:49 PM #148
Re: Refrigeration 101
hello im a newbie..i'll will enjoy this such a helpful tips on my work and profession..
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15-10-2010, 02:42 PM #149
Refrigeration and positive/megative air pressure
Hi, i am just starting to learn about refrigeration and how it all works, although i am unsure of how positive and negative air pressure will affect a refrigeration system i was hoping that some1 could help me out with this.
I am currently designing a filtered positive air system for a food production plant, up to now the positive air systems i have installed have been fed from the outside ambient air. on this system as the production room is to be kept at below 12degrees celsius and is 700cubic metres, going on the basis of using 8 air changes per hour. i am hoping to use two feeds with dampers, one from the outside and one from the refrigerated garage store next door to the production room which is kept at 5 degrees is 2,800 cubic metres. Will the negative air pressure created in the refrigerated garage area (which is 4x the size of the production room) affect the evaporators in this room, apart from making them work a little harder?? i am sorry if i havn't explained this very well this is my fist time writing a post. i can give more details if needed. Hope some one can advise. Thanks
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19-10-2010, 03:17 AM #150
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