Freeze Dryer Chamber

[80Builder80]

The propriety controller and automation is something I didn’t want to simulate. Automating the process would be far down the road. My goal would be just to get it to work. Temps and vacuum would be monitored and activated manually based off of times that others have observed. From what I’ve read online, the freeze time takes about 9 hours. Once that time frame has been reached, I would manually turn on the vacuum. Once the appropriate vacuum was reached, I would turn on the heaters which are run by a timer and thermometer based on times and temps observed by others. No humidity sensors. I would test the food once the observed times had expired and run longer if needed.

One of the guys I worked with years ago started and owns Harvest Right. The idea is not new nor is the equipment. The controller and the algorithm to control everything is the key and it is very proprietary. There is nothing really new with what they do. As BBeerme said, just SCR driven heater plates, relay for the vac pump, and relay for the compressor, all fed by a very intuitive vacuum sensor. Chamber is first pulled down to temp, then placed under vacuum for a specific amount of time, then heaters are slowly brought up to release moisture at a very controlled rate. The rate is dictated by the climb in microns thus if they climb too high the heaters are backed off if they climb too slow, the heaters are ramped up. That was about all I cared to learn from my visit. I was there to buy some already freeze dried food for a long hiking trip I had with some friends, this is where I ran into my old co-worker the owner and he showed me a few thing. It is not as easy as anyone thinks and takes a verrrrry long time just to do a batch of your own stuff.

[BBeerme]

Nope.

Your shelf temp should governed by your micron reading.

The propriety controller and automation is something I didn’t want to simulate. Automating the process would be far down the road. My goal would be just to get it to work. Temps and vacuum would be monitored and activated manually based off of times that others have observed. From what I’ve read online, the freeze time takes about 9 hours. Once that time frame has been reached, I would manually turn on the vacuum. Once the appropriate vacuum was reached, I would turn on the heaters which are run by a timer and thermometer based on times and temps observed by others. No humidity sensors. I would test the food once the observed times had expired and run longer if needed.

[80Builder80]

Unfortunately I don’t have a way of automating that process. I can however automate the on/off of the heaters based on temp and time from observations of others. From those observations, once the appropriate vacuum is reached, the heaters are on for about 5 minutes while reaching 50 degrees then off for 20. This cycling goes on for several hours. Then the heaters run 5 minutes on, 5 minutes off for a period of time until the remaining moisture level (or lack of moisture) is reached. Then the system shuts down. Since I won’t be able to monitor moisture internally at this time, I’ll have to remove it, test it, and run longer if needed. I’m also trying to stay under 1/3 of the cost of the retail price. Once I get the system to work, I may look at adding more monitoring and automation.

So, as far as the compressor, would I be fine with purchasing a new no charge 134a compressor and charging it with 410a? I don’t want to blow out the compressor. Especially if I’m buying a new one.

Nope.

Your shelf temp should governed by your micron reading.

[BBeerme]

You do not need to automate that process. I already explained it to you. Go back and re-read this thread.

This post of yours tells me you do not yet understand the freeze drying process.

Unfortunately I don’t have a way of automating that process. I can however automate the on/off of the heaters based on temp and time from observations of others. From those observations, once the appropriate vacuum is reached, the heaters are on for about 5 minutes while reaching 50 degrees then off for 20. This cycling goes on for several hours. Then the heaters run 5 minutes on, 5 minutes off for a period of time until the remaining moisture level (or lack of moisture) is reached. Then the system shuts down. Since I won’t be able to monitor moisture internally at this time, I’ll have to remove it, test it, and run longer if needed. I’m also trying to stay under 1/3 of the cost of the retail price. Once I get the system to work, I may look at adding more monitoring and automation.

So, as far as the compressor, would I be fine with purchasing a new no charge 134a compressor and charging it with 410a? I don’t want to blow out the compressor. Especially if I’m buying a new one.

[80Builder80]

You are correct. I do not understand the entire detailed science behind the freeze drying or lyophilization process. I understand that there is a corolation between temperature and vacuum where water goes from vapor to solid in the sublimation process. I understand that this requires heat to be applied to the material in order to facilitate that process. I also understand that commercial available equipment have the ability to monitor temperature, vacuum, moisture levels, among other environmental factors and adjust the process based on those conditions. I am trying to learn this process by experimenting and adjusting as I go. I am still in the early stages of this process.

I am using Harvest Right as reference material based off the information that is out there and replicating that as best I can with what information I have access to. There are serval individuals that have documented what the machine is doing during it's run cycle and I am using that information to start with. This information includes what temp the chamber is getting to and how long it takes to get there. When the vacuum pump turns on and how long it takes to pull the appropriate vacuum. When the heaters turn on, what shelf temp they maintain, and the times for the on/off cycles. I'm sure that Harvest Right is using other monitoring methods to achieve the results. However, I am working with what I have access to and my current abilities and knowledge base.

I chose my chamber based on their chamber size. I have the same volume. I chose my vacuum pump based off of the recommended pump. My chamber will pull and hold a deep vacuum. I built my rack system to apply the observed temps to the material. I have thermometers and times to control and maintain the heat to the material.

My primary concern is achieving the proper chamber temp. As I explain before, my experience is technician based. Simple repair and maintenance. Replacing equipment as needed with like equipment. Hence my original question. My goal is to reach a desired chamber temp range at least -20 but a preferred temp of >-30. I have 410a on hand and this is what they are using. I am needing a recommendation for a compressor that can handle 410a.

This post of yours tells me you do not yet understand the freeze drying process.

increase of shelf temp will show a rise of microns. No other shelf temp is increased until that same low vacuum is achieved. Used to all be manual adjustments, but now there are controllers to do that.

Wouldn't the use of controllers make the process automated?

[heatingman]

Seems like a whole lot of extra effort for a couple extra years shelf life.

Why not just dehydrate the food?

Im no expert, but according the interweb, your gain is a couple extra years shelf storage time.

Like 20-25 years for dried goods vs 25 to 30 for freeze dried.

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[80Builder80]

I've never heard of dehydrated foods lasting 20+ years. I do dehydrate too. But I'm also after the reconstitution of the food and nutrition. Dehydrated food can not be reconstituted to close to original and the hydration process depletes the nutrition of the food. Freeze dried foods can be reconstituted to near original with minimal nutrition loss.

Seems like a whole lot of extra effort for a couple extra years shelf life.

Why not just dehydrate the food?

Im no expert, but according the interweb, your gain is a couple extra years shelf storage time.

Like 20-25 years for dried goods vs 25 to 30 for freeze dried.

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[BBeerme]

First let me commend you on your efforts. I played around with so much stuff, doing much of what you are doing, on the customers dime. Because that customer was in Silicone Valley and trying to out do that company across the street.

That being said, I've never heard of humidity being monitored in a freeze drier. Things may have changed. But for where you are at, shelf temp will (should) be controlled by the vacuum in the chamber alone. Nothing else. Understand the basics and do not over think this.

You are correct. I do not understand the entire detailed science behind the freeze drying or lyophilization process. I understand that there is a corolation between temperature and vacuum where water goes from vapor to solid in the sublimation process. I understand that this requires heat to be applied to the material in order to facilitate that process. I also understand that commercial available equipment have the ability to monitor temperature, vacuum, moisture levels, among other environmental factors and adjust the process based on those conditions. I am trying to learn this process by experimenting and adjusting as I go. I am still in the early stages of this process.

I am using Harvest Right as reference material based off the information that is out there and replicating that as best I can with what information I have access to. There are serval individuals that have documented what the machine is doing during it's run cycle and I am using that information to start with. This information includes what temp the chamber is getting to and how long it takes to get there. When the vacuum pump turns on and how long it takes to pull the appropriate vacuum. When the heaters turn on, what shelf temp they maintain, and the times for the on/off cycles. I'm sure that Harvest Right is using other monitoring methods to achieve the results. However, I am working with what I have access to and my current abilities and knowledge base.

I chose my chamber based on their chamber size. I have the same volume. I chose my vacuum pump based off of the recommended pump. My chamber will pull and hold a deep vacuum. I built my rack system to apply the observed temps to the material. I have thermometers and times to control and maintain the heat to the material.

My primary concern is achieving the proper chamber temp. As I explain before, my experience is technician based. Simple repair and maintenance. Replacing equipment as needed with like equipment. Hence my original question. My goal is to reach a desired chamber temp range at least -20 but a preferred temp of >-30. I have 410a on hand and this is what they are using. I am needing a recommendation for a compressor that can handle 410a.



Wouldn't the use of controllers make the process automated?

[80Builder80]

Let's pretend that my question about what compressor to use has nothing to do with the freeze drying process. Let's pretend it has to do with modifying a regular upright freezer.

I have a Fridgidaire 20 cu ft upright freezer Model #LFFH20F3QM2. It easily maintains a temp of -10 charged with 134a. That's not good enough for me because I like the extreme in everything. I want this thing to hit -50. Can I evac the 134a, flush the system and drop in 410a without issue? Or do I need to change out the compressor? If a change out is required. What would be your recommendation for compressor that would not require any more, or not much more, space in the cabinet?

[BBeerme]

The bore and stroke are different on compressors made for those refrigerants. I think the 410 compressor has a larger bore and shorter stroke, but it's been many years since I learned which was which. Since you'll be dealing with the extreme low end of things, probably wouldn't make much difference in the life of the compressor. Meaning, compressors made for 410 are typically going to be made for air conditioning, which means they are designed to work with 80*F return air temp and in ambients of 100*F which would be pushing 450-500 psig.

If you were to put 410 in a compressor designed for 134, and keep the suction around 10-15 psig, your head would probably be in the range of 200-225. It would take some tinkering around with evap and cap tube sizing to get the proper cooling back to the compressor. Remember, every time you drop further in temp, compressor capacity goes down as well. And you will need cooling back to the compressor in order to have a long compressor life.

You will want the suction line temp at compressor inlet no warmer than 65*F. Cooler is better, but that is the design threshold.

[heatingman]

Id be most concerned about start up / initial pull down pressures using 410 in a 134a compressor. Metering device sized for ultra low temp could easily create significant high side pressure at start up.

Im not certain but I imagine they may use thinner wall thickness and such in a 134a compressor cause they can get away with it.

Might get away with it, I just dont know.


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[BBeerme]

Pretty sure I mentioned earlier that a CPR would be required.

Been thinking about his cap tube sizing problem, gonna take a lot of experimentation to get it right. Not to mention the cold coil sizing. Then it occurred to me that to eliminate all of the time sizing the cap tube, to just use an AEV (automatic expansion valve). Then you could dial in whatever suction pressure you wanted.

Id be most concerned about start up / initial pull down pressures using 410 in a 134a compressor. Metering device sized for ultra low temp could easily create significant high side pressure at start up.

Im not certain but I imagine they may use thinner wall thickness and such in a 134a compressor cause they can get away with it.

Might get away with it, I just dont know.


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[jimp]

I have worked on a lot of freeze dryers over the last thirty years. What you're building sounds like a thirty year old design.

[stumpdigger]

Unfortunately I don’t have a way of automating that process. I can however automate the on/off of the heaters based on temp and time from observations of others. From those observations, once the appropriate vacuum is reached, the heaters are on for about 5 minutes while reaching 50 degrees then off for 20. This cycling goes on for several hours. Then the heaters run 5 minutes on, 5 minutes off for a period of time until the remaining moisture level (or lack of moisture) is reached. Then the system shuts down. Since I won’t be able to monitor moisture internally at this time, I’ll have to remove it, test it, and run longer if needed. I’m also trying to stay under 1/3 of the cost of the retail price. Once I get the system to work, I may look at adding more monitoring and automation.

So, as far as the compressor, would I be fine with purchasing a new no charge 134a compressor and charging it with 410a? I don’t want to blow out the compressor. Especially if I’m buying a new one.

NO, you cannot take a low pressure compressor and turn it into a high pressure compressor, period. Use 408A, connect it to an R-22 compressor, about a 3 ton, you do the math but 3X at least. Use a TXV!!! with adjustable SH, (cap tube? you are out of your mind, sue me). That's what you want to know.
I replaced a lot of dead R12 units with R409A and an r22 compressor , and they all worked just fine.

[80Builder80]

This is the machine I am referencing.



This is the compressor.



It is not my intent to argue about your statement but that is a cap tube. There is no visible TXV unless it is out of view.

This is a quote from their information that I came across:

"While a variety of refrigerants might be used, a vapor pressure differential between −55° F. and 100° F. of at least 230 pounds per inch2 (psi), such as at least 300 psi, assists in enabling a temperature in chamber 302 of −50° F. with single-stage compression. Also, the refrigerant may exhibit a vapor pressure at −50° F. of at least 14.7 psi absolute to ensure a vapor pressure above atmospheric pressure at a suction line to compressor 406. One example of a suitable refrigerant includes a 50/50 weight percent combination of HFC-32 (difluoromethane) and HFC-125 (pentafluoroethane) sold under the trade name AZ-20 and covered by U.S. Pat. No. 4,978,467. R-410A is known for use in air conditioning applications and exhibits a vapor pressure differential between −55° F. and 100° F. of about 315 psi and a vapor pressure at −50° F. of about 19 psi absolute.

Given the single-stage compression, the selected refrigerant, and expected operating conditions, a design for refrigeration system 400 includes selecting an inside diameter and a length for capillary tube 410 suitable to produce the desired chamber temperature. While a smaller inside diameter affords increased pressure drop, it also produces decreased flow rate and, thus, cooling capacity. A longer length also affords increased pressure drop, accordingly, capillary tube length may be at least 30 inches, such as 30 to 70 inches, and a nominal inside diameter may be at least 0.024 inches. A capillary tube with an inside diameter of 0.032 inches may have a length of 48 inches."

NO, you cannot take a low pressure compressor and turn it into a high pressure compressor, period. Use 408A, connect it to an R-22 compressor, about a 3 ton, you do the math but 3X at least. Use a TXV!!! with adjustable SH, (cap tube? you are out of your mind, sue me). That's what you want to know. I replaced a lot of dead R12 units with R409A and an r22 compressor , and they all worked just fine.

[BBeerme]

Sounds like something from patent info.

[exbrown]

These Harvest Right controllers may be of interest to you.

Unused HARVEST RIGHT FREEZE DRYER ?? CPU Harvest Right # 102214H Purchased 2020

Sorry, I cannot post the entire link.

ebay.com/itm/Unused-HARVEST-RIGHT-FREEZE-DRYER-CPU-Harvest-Right-102214H-Purchased-2020-/373050182224?mkcid=16&mkevt=1&_trksid=p2349624.m46 890.l49286&mkrid=711-127632-2357-0