Homemade Heat Pump Clothes Dryer - Page 4

Daox · 06-22-15, 10:30 AM

http://ecorenovator.org/forum/geothe...ood-dryer.html

jeff5may · 06-22-15, 10:53 AM

http://ecorenovator.org/forum/geothe...ood-dryer.html

The principles of operation for these two units are closely related. The main difference being the time frame: most Americans are not highly patient with clothes dryers. We also tend to dry our clothes completely in the tumbler. This is the main reason they use so much power so fast. Spread out the time frame a bit, and a clothes dryer is just a large dehydration unit.

Jake is building a custom phase change unit as I write this. As of last night, he had not built a drying chamber. If this project progresses as fast as his, he could definitely stand to learn from your trials. However, he is a speed demon, and might not wait for your results.

There have been some previous discussions on this very topic, but none of them took the analytical approach you are pursuing. Regardless of what Jake does, many of us will benefit from your results. Keep it going strong, brother!

MEMPHIS91 · 06-22-15, 09:58 PM

Quote:

Originally Posted by jeff5may

http://ecorenovator.org/forum/geothe...ood-dryer.html

The principles of operation for these two units are closely related. The main difference being the time frame: most Americans are not highly patient with clothes dryers. We also tend to dry our clothes completely in the tumbler. This is the main reason they use so much power so fast. Spread out the time frame a bit, and a clothes dryer is just a large dehydration unit.

Jake is building a custom phase change unit as I write this. As of last night, he had not built a drying chamber. If this project progresses as fast as his, he could definitely stand to learn from your trials. However, he is a speed demon, and might not wait for your results.

There have been some previous discussions on this very topic, but none of them took the analytical approach you are pursuing. Regardless of what Jake does, many of us will benefit from your results. Keep it going strong, brother!

HAHA speed demon. Thanks. Well I got very side tracked on this build, I have been more or less using it as a test dummy.

Xzeption, I LOVE the work being done here, it has already provided good information. I'm on the edge of my seat to see how it turns out.

Xzeption · 06-29-15, 08:48 PM

Here are my results from my two most recent tests.

On 6/24 the only change I made was the dehumidifier fan switch from low to high. I was concerned that the previous test did not provide enough data as I both air sealed and toggled the dehumidifier switch. Here are the results.
Mass in: 1392 g
Mass out: 1104 g
water removed: 288 g (~43%)
water in bin: 35 g

On 6/28 I came up with a better latch system in the pic. I used three tie downs to secure the door and maintain a pressure seal. I did notice a bit of warm air coming out the corner, but much less than before. The dehumidifier fan was set to low speed. I forgot to turn the box fan on until 20 minutes through the 60 minute test. This explains the reduced drying, but I want to run this test again for better data.
Mass in: 1458 g
Mass out: 1247 g
water removed: 211 g (~29%)
water in bin: 44 g
I expected before this test that the dehumidifier fan on low speed would have significantly more water in the bin. Until I try this with the box fan on the whole time I am inconclusive.

I am having trouble seeing trends in the data. The statistician in me screams "I NEED MORE DATA!" This is the first time I have played with a dehumidifier and it is falling under suspicion. It is rated 50 pints / (24 hours) which should be about 1 liter / hour in design conditions. Yet it is not getting a tenth of that. Time for me to read the "Heat Pumps for Dummies" thread!

AC_Hacker · 06-30-15, 11:08 AM

Quote:

Originally Posted by Xzeption

...Yet it is not getting a tenth of that. Time for me to read the "Heat Pumps for Dummies" thread!

I hope you find what you're looking for in that thread, but I don't think that it's very well developed. Hopefully, by posting questions there, and getting answers, you will help to build it out.

Getting back to your project here, could you post a diagram of how air flows in your dryer... or how you wish it would flow?

There could be a clue there.

-AC

Xzeption · 07-05-15, 08:00 PM

I have not made any changes to my setup in the past few cycles, so the measurements have not changed much. This helps me build a baseline for future adjustments. I won't bore readers with repeated numbers, so I will follow AC_Hacker's suggestion of an airflow diagram. I drew on an older photo as I currently have it closed and running.

Everything is in a single cabinet. The box fan at the top is pointed down and should ensure the air is well mixed. The dehumidifier should take in moist air and output hotter drier air. The drier air plus the air velocity from the box fan should evaporate moisture from the cloth. Of course my understanding may be flawed.

AC_Hacker · 07-06-15, 12:05 PM

Thanks for posting the diagram, it would be interesting to know if the air actually flowed in the way that you wish it to flow.

There is a possibility that the box fan doesn't really help, and only adds to the energy used.

* * *

In thinking about your project, it occurred to me that it would be useful to have bench-marks against which you could measure your progress. One benchmark would be a worst-case benchmark (Red Dot) in which the user cares nothing about energy efficiency, and only about the shortest possible time needed to dry clothes. As seen from this perspective, electric-resistance dryers are a spectacular success... they use Tons of energy, and the clothes are dried very quickly.

Another, best-case benchmark (Green Dot), would be line drying, which would use no manufactured energy, but would take a long time. Polish EcoRenovator, Piwoslaw gave us the example of how clothes drying in his part of the world was accomplished by setting aside an area inside a house where clothes could be hung to dry. As I recall, there was a photograph in his post that showed that there were sun-facing windows in that room. Another spectacular success.

A bench-mark between these extremes (Blue Dot), would be heat-pump dryers, that shorten the time for clothes to dry, and also use less energy than the rapacious electric resistance dryers.

* * *

Maybe consider the idea that manufactured dryers have the benefit of having previous engineering and testing incorporated into their design, some of which could be useful to you.

Tumbling action, for instance... I really do not like the fact that tumbling action shortens the life of fabrics because of the constant beating that clothes are subject to.

However, the tumbling action does help expose the moisture in the fabric to the lower-humidity air flow.

There might be another advantage to the design of manufactured dryers, in as much as the airflow has been almost certainly analyzed and optimally designed.

* * *

But getting back to your air flow... you are using a packaged de-humidifier, that draws in air with a higher moisture content, and then expels air with a lower moisture content. There is a distinct possibility that as your project now exists, the de-humidifier just might be largely recycling most of it's own output, without passing that air over the clothing.

It could help the project if you could arrange so that the clothes were subjected to only the lower-moisture that is exiting air from the de-humidifier, and then only the air that had already made the journey passed the clothes, could re-enter the de-humidifier.

Maybe some kind of clever baffle could accomplish this inside the box.

Best,

-AC

MN Renovator · 07-07-15, 09:38 PM

Based on my own experience with using a dehumidifier in an ineffective way, I found out that there is a harsh limit to the dehumidification that can be accomplished if the device is located in an area too warm. Once the ambient temperature that the dehumidifier is operating in is too warm, the dehumidifier will run constantly but its evaporator coil will never get cold enough to dehumidify well and then ends up humming along without getting a cold enough evaporator surface temperature to continue effectively dehumidifying the air. The experience I had with mine is that anything too warm for it to trip into a defrost cycle periodically(even if that means once every 2 hours briefly) the unit would fail to do its job.

By enclosing the whole thing, you might just be putting your clothes into a hot space heated chamber where the dew point rises in the box where the dehumidifier is unable to cool its coil enough to remove the moisture effectively.

I could be wrong but a suggestion might be to connect a temp probe to the evap coil to make sure you are getting a drop to the 30s or 40s. Granted even 50s or perhaps 60s might do the job but eventually once the clothes are dried slightly, I'd hope the dew point(evap coil temp) would drop to 50s or lower otherwise you are trapping them in a moist hot box.

I hope this helps.

MEMPHIS91 · 07-08-15, 09:35 PM

Quote:

Originally Posted by MN Renovator

Based on my own experience with using a dehumidifier in an ineffective way, I found out that there is a harsh limit to the dehumidification that can be accomplished if the device is located in an area too warm. Once the ambient temperature that the dehumidifier is operating in is too warm, the dehumidifier will run constantly but its evaporator coil will never get cold enough to dehumidify well and then ends up humming along without getting a cold enough evaporator surface temperature to continue effectively dehumidifying the air. The experience I had with mine is that anything too warm for it to trip into a defrost cycle periodically(even if that means once every 2 hours briefly) the unit would fail to do its job.

This is EXACTLY what I'm finding with my food dryer. I can hit those nice high temps at 130F+ but I'm not pulling the moisture any lower. When the air temp in the box is below 95F the evap coil pulls moisture down as low as 12%. Heat is not as important as dew point.

Xzeption · 07-26-15, 07:15 PM

My AC went out for a week, so I've had to shelve this project. I'll still be collecting data to establish a base line, but no changes will be made until I get my HVAC system replaced. Fortunately all my heat pump reading at ecorenovator will be paying off

Thanks MN Renovator, I will definitely be looking into dehumidifier limits and the "moist hot box" issue.

06-22-15, 10:30 AM	#31
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	http://ecorenovator.org/forum/geothe...ood-dryer.html __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

06-29-15, 08:48 PM	#34
Xzeption Lurking Renovator Join Date: May 2015 Location: Raleigh, NC Posts: 12 Thanks: 1 Thanked 2 Times in 2 Posts	Here are my results from my two most recent tests. On 6/24 the only change I made was the dehumidifier fan switch from low to high. I was concerned that the previous test did not provide enough data as I both air sealed and toggled the dehumidifier switch. Here are the results. Mass in: 1392 g Mass out: 1104 g water removed: 288 g (~43%) water in bin: 35 g On 6/28 I came up with a better latch system in the pic. I used three tie downs to secure the door and maintain a pressure seal. I did notice a bit of warm air coming out the corner, but much less than before. The dehumidifier fan was set to low speed. I forgot to turn the box fan on until 20 minutes through the 60 minute test. This explains the reduced drying, but I want to run this test again for better data. Mass in: 1458 g Mass out: 1247 g water removed: 211 g (~29%) water in bin: 44 g I expected before this test that the dehumidifier fan on low speed would have significantly more water in the bin. Until I try this with the box fan on the whole time I am inconclusive. I am having trouble seeing trends in the data. The statistician in me screams "I NEED MORE DATA!" This is the first time I have played with a dehumidifier and it is falling under suspicion. It is rated 50 pints / (24 hours) which should be about 1 liter / hour in design conditions. Yet it is not getting a tenth of that. Time for me to read the "Heat Pumps for Dummies" thread! Attached Thumbnails __________________ There is an exception to every rule. Including this one. I wish my country would switch to the metric system. My apologies to international readers who see me jump between metric and imperial units. Last edited by Daox; 06-30-15 at 02:26 PM..

07-05-15, 08:00 PM	#36
Xzeption Lurking Renovator Join Date: May 2015 Location: Raleigh, NC Posts: 12 Thanks: 1 Thanked 2 Times in 2 Posts	I have not made any changes to my setup in the past few cycles, so the measurements have not changed much. This helps me build a baseline for future adjustments. I won't bore readers with repeated numbers, so I will follow AC_Hacker's suggestion of an airflow diagram. I drew on an older photo as I currently have it closed and running. Everything is in a single cabinet. The box fan at the top is pointed down and should ensure the air is well mixed. The dehumidifier should take in moist air and output hotter drier air. The drier air plus the air velocity from the box fan should evaporate moisture from the cloth. Of course my understanding may be flawed. Attached Thumbnails __________________ There is an exception to every rule. Including this one. I wish my country would switch to the metric system. My apologies to international readers who see me jump between metric and imperial units.

07-06-15, 12:05 PM	#37
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Thanks for posting the diagram, it would be interesting to know if the air actually flowed in the way that you wish it to flow. There is a possibility that the box fan doesn't really help, and only adds to the energy used. * * * In thinking about your project, it occurred to me that it would be useful to have bench-marks against which you could measure your progress. One benchmark would be a worst-case benchmark (Red Dot) in which the user cares nothing about energy efficiency, and only about the shortest possible time needed to dry clothes. As seen from this perspective, electric-resistance dryers are a spectacular success... they use Tons of energy, and the clothes are dried very quickly. Another, best-case benchmark (Green Dot), would be line drying, which would use no manufactured energy, but would take a long time. Polish EcoRenovator, Piwoslaw gave us the example of how clothes drying in his part of the world was accomplished by setting aside an area inside a house where clothes could be hung to dry. As I recall, there was a photograph in his post that showed that there were sun-facing windows in that room. Another spectacular success. A bench-mark between these extremes (Blue Dot), would be heat-pump dryers, that shorten the time for clothes to dry, and also use less energy than the rapacious electric resistance dryers. * * * Maybe consider the idea that manufactured dryers have the benefit of having previous engineering and testing incorporated into their design, some of which could be useful to you. Tumbling action, for instance... I really do not like the fact that tumbling action shortens the life of fabrics because of the constant beating that clothes are subject to. However, the tumbling action does help expose the moisture in the fabric to the lower-humidity air flow. There might be another advantage to the design of manufactured dryers, in as much as the airflow has been almost certainly analyzed and optimally designed. * * * But getting back to your air flow... you are using a packaged de-humidifier, that draws in air with a higher moisture content, and then expels air with a lower moisture content. There is a distinct possibility that as your project now exists, the de-humidifier just might be largely recycling most of it's own output, without passing that air over the clothing. It could help the project if you could arrange so that the clothes were subjected to only the lower-moisture that is exiting air from the de-humidifier, and then only the air that had already made the journey passed the clothes, could re-enter the de-humidifier. Maybe some kind of clever baffle could accomplish this inside the box. Best, -AC Attached Thumbnails __________________ I'm not an HVAC technician. In fact, I'm barely even a hacker...

07-26-15, 07:15 PM	#40
Xzeption Lurking Renovator Join Date: May 2015 Location: Raleigh, NC Posts: 12 Thanks: 1 Thanked 2 Times in 2 Posts	My AC went out for a week, so I've had to shelve this project. I'll still be collecting data to establish a base line, but no changes will be made until I get my HVAC system replaced. Fortunately all my heat pump reading at ecorenovator will be paying off Thanks MN Renovator, I will definitely be looking into dehumidifier limits and the "moist hot box" issue. __________________ There is an exception to every rule. Including this one. I wish my country would switch to the metric system. My apologies to international readers who see me jump between metric and imperial units.

06-22-15, 10:53 AM	#32
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	http://ecorenovator.org/forum/geothe...ood-dryer.html The principles of operation for these two units are closely related. The main difference being the time frame: most Americans are not highly patient with clothes dryers. We also tend to dry our clothes completely in the tumbler. This is the main reason they use so much power so fast. Spread out the time frame a bit, and a clothes dryer is just a large dehydration unit. Jake is building a custom phase change unit as I write this. As of last night, he had not built a drying chamber. If this project progresses as fast as his, he could definitely stand to learn from your trials. However, he is a speed demon, and might not wait for your results. There have been some previous discussions on this very topic, but none of them took the analytical approach you are pursuing. Regardless of what Jake does, many of us will benefit from your results. Keep it going strong, brother!

07-07-15, 09:38 PM	#38
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	Based on my own experience with using a dehumidifier in an ineffective way, I found out that there is a harsh limit to the dehumidification that can be accomplished if the device is located in an area too warm. Once the ambient temperature that the dehumidifier is operating in is too warm, the dehumidifier will run constantly but its evaporator coil will never get cold enough to dehumidify well and then ends up humming along without getting a cold enough evaporator surface temperature to continue effectively dehumidifying the air. The experience I had with mine is that anything too warm for it to trip into a defrost cycle periodically(even if that means once every 2 hours briefly) the unit would fail to do its job. By enclosing the whole thing, you might just be putting your clothes into a hot space heated chamber where the dew point rises in the box where the dehumidifier is unable to cool its coil enough to remove the moisture effectively. I could be wrong but a suggestion might be to connect a temp probe to the evap coil to make sure you are getting a drop to the 30s or 40s. Granted even 50s or perhaps 60s might do the job but eventually once the clothes are dried slightly, I'd hope the dew point(evap coil temp) would drop to 50s or lower otherwise you are trapping them in a moist hot box. I hope this helps.