Heat Pump Food Dryer - Page 2

AC_Hacker · 06-20-15, 11:03 AM

Quote:

Originally Posted by MEMPHIS91

It started poring water out with in 5 minutes of running. But I think my cap tube is to long so I'm going to cut some off and see what happens.

I thought that pouring water out was what you wanted??

-AC

MEMPHIS91 · 06-20-15, 12:27 PM

Doax, yeah I really enjoy this type of work.

AC, sorry I didn't make that clearer. It is what I want, but the discharge pressure is higher than I want and the suction temp is 80F.

jeff5may · 06-20-15, 11:13 PM

Your discharge pressure is not all that high for r22 or r290. Unless you have too much airflow, you could stand to add some charge. A shorter cap tube will cause your unit to draw more power. Most dehumidification units run up to 200 - 250 psi before the evaporator frosts up.

180 psig translates to 103 degf saturation temp in the condenser. Not bad for a window ac unit in a mild climate, but not high enough to dehydrate food. Most dehydrators run above 110, and top out around 150 on the thermostat. To get that high, you will need 300+ psig in the condenser. No two ways about it.

Before you go hog wild on this one, tell us the model of the compressor. I saw the bar code label in one pic, but there is not enough detail to make out anything but the LG logo. The compressor you have looks like a larger version of the one in my "hacker vacu-claimer". It was the condensing unit in a side-by-side fridge that rusted out from old age and condensation. Now it reclaims refrigerant and pulls vacuum on my experimental rigs.

I am eager to see what type of drying box you construct, as I may build a similar unit this year. my parents and one of their tenants planted way too many tomatoes and peppers this year, and the tenants don't know what they are doing. I doubt from the current level of involvement that they know how to can properly, or that they will ante up for mason jars. We have a few of the round tower (American Harvest and imitators) dehydrators, but they will definitely not be able to digest the harvest come August.

MEMPHIS91 · 06-22-15, 10:05 PM

Jeff, I am still playing with the cap tube sizing/charge. I have swapped out to a 8.5 LRA compressor as well. It pulls 1.3 amps with the same pressures. I will get pictures up soon and more details. I am also considering using R152A and R290 mixed. The research I have done shows that the mix is close to R12, if so I should be able to get colder than just R290.

AC_Hacker · 06-22-15, 11:03 PM

Quote:

Originally Posted by MEMPHIS91

... I am also considering using R152A and R290 mixed. The research I have done shows that the mix is close to R12, if so I should be able to get colder than just R290.

You might also look into Iso-Butane. I have not worked with it, but I know it has sometimes been used as a substitute for R12.

https://en.wikipedia.org/wiki/Isobutane

-AC

jeff5may · 06-23-15, 08:00 AM

Running a blend really throws some engineering into the works. Yes, you will lower your working pressures, but then the compressor might not have enough displacement or suction pressure. Pots made for R12/R134a are built with more displacement and lower compression ratio than those for R22/R290.

MEMPHIS91 · 06-23-15, 10:35 AM

AC yes I did look into that. I am going to try it at some point too.

Jeff yes this comp was meant for 134a so I'm hoping it will make things run even better. I am trying to learn the relationships of all the different variables. Like different gases and cap tubes. Different size and type condensers and evaporators. Different size and type compressors and gases, and different pressures. Until I'm able to see each one work or fail it's hard to get in my brain, guessing is not the point here but it does tell me more about phase charge in general. I am taking pictures and recording data as I go.
What would be your thoughts on a TXV in this system? I know you added one to a larger dehumidifier.

jeff5may · 06-23-15, 12:15 PM

For this size of rig, if you are using a pot made for 134a, I personally would hit up the discount outlets and find some 134a. We have value city and big lots here, your location may vary. I found it for like 6 bucks a can for plain Jane, super cool was maybe 8. Super cool is regular 134a with some butane and propane or ether blended in. If you run a txv, match it to the compressor and the gas. Charge by measuring subcooling at the exit of the condenser, and make sure to have some extra space for excess liquid refrigerant to buffer and not cause trouble.

MEMPHIS91 · 06-23-15, 05:33 PM

PANASONIC DC57C84RCU6 SPECIFICATION SHEET Pdf Download. is what found for the compressor I have on there now.

I'll start looking for a txv that small. Do they make them that small?

jeff5may · 06-23-15, 11:07 PM

Quote:

Originally Posted by MEMPHIS91

PANASONIC DC57C84RCU6 SPECIFICATION SHEET Pdf Download. is what found for the compressor I have on there now.

I'll start looking for a txv that small. Do they make them that small?

That's an itty bitty little compressor. It might do the job, but its eer spec is like 5 or 7, so it isn't much more efficient than a toaster oven. Uses less power, though.

06-20-15, 11:13 PM	#13
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Your discharge pressure is not all that high for r22 or r290. Unless you have too much airflow, you could stand to add some charge. A shorter cap tube will cause your unit to draw more power. Most dehumidification units run up to 200 - 250 psi before the evaporator frosts up. 180 psig translates to 103 degf saturation temp in the condenser. Not bad for a window ac unit in a mild climate, but not high enough to dehydrate food. Most dehydrators run above 110, and top out around 150 on the thermostat. To get that high, you will need 300+ psig in the condenser. No two ways about it. Before you go hog wild on this one, tell us the model of the compressor. I saw the bar code label in one pic, but there is not enough detail to make out anything but the LG logo. The compressor you have looks like a larger version of the one in my "hacker vacu-claimer". It was the condensing unit in a side-by-side fridge that rusted out from old age and condensation. Now it reclaims refrigerant and pulls vacuum on my experimental rigs. I am eager to see what type of drying box you construct, as I may build a similar unit this year. my parents and one of their tenants planted way too many tomatoes and peppers this year, and the tenants don't know what they are doing. I doubt from the current level of involvement that they know how to can properly, or that they will ante up for mason jars. We have a few of the round tower (American Harvest and imitators) dehydrators, but they will definitely not be able to digest the harvest come August. Last edited by jeff5may; 06-21-15 at 08:04 AM..

06-20-15, 12:27 PM	#12
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Doax, yeah I really enjoy this type of work. AC, sorry I didn't make that clearer. It is what I want, but the discharge pressure is higher than I want and the suction temp is 80F.

06-22-15, 10:05 PM	#14
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Jeff, I am still playing with the cap tube sizing/charge. I have swapped out to a 8.5 LRA compressor as well. It pulls 1.3 amps with the same pressures. I will get pictures up soon and more details. I am also considering using R152A and R290 mixed. The research I have done shows that the mix is close to R12, if so I should be able to get colder than just R290.

06-23-15, 08:00 AM	#16
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Running a blend really throws some engineering into the works. Yes, you will lower your working pressures, but then the compressor might not have enough displacement or suction pressure. Pots made for R12/R134a are built with more displacement and lower compression ratio than those for R22/R290.

06-23-15, 10:35 AM	#17
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	AC yes I did look into that. I am going to try it at some point too. Jeff yes this comp was meant for 134a so I'm hoping it will make things run even better. I am trying to learn the relationships of all the different variables. Like different gases and cap tubes. Different size and type condensers and evaporators. Different size and type compressors and gases, and different pressures. Until I'm able to see each one work or fail it's hard to get in my brain, guessing is not the point here but it does tell me more about phase charge in general. I am taking pictures and recording data as I go. What would be your thoughts on a TXV in this system? I know you added one to a larger dehumidifier.

06-23-15, 12:15 PM	#18
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	For this size of rig, if you are using a pot made for 134a, I personally would hit up the discount outlets and find some 134a. We have value city and big lots here, your location may vary. I found it for like 6 bucks a can for plain Jane, super cool was maybe 8. Super cool is regular 134a with some butane and propane or ether blended in. If you run a txv, match it to the compressor and the gas. Charge by measuring subcooling at the exit of the condenser, and make sure to have some extra space for excess liquid refrigerant to buffer and not cause trouble.

06-23-15, 05:33 PM	#19
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	PANASONIC DC57C84RCU6 SPECIFICATION SHEET Pdf Download. is what found for the compressor I have on there now. I'll start looking for a txv that small. Do they make them that small?