heat pump tumble dryer

[admin]

Hi: clever dicky
1. “Heatpumps generally are VERY efficient when running but do take a while to get going. They use a lot of power to get the process started because you also need a high heat source (not only in terms of temperature but mainly quantity) to get the process going to evaporate the water vapour.”
I don’t think so. The air conditioner only takes very less time to produce hot air. Can you explain more detail?

2. “Down sides are many, and believe me I know. The biggest is the mechanical damage caused. Because there is little absolute control, once the process starts it can tend to cascade.”
The air conditioner has no this problem. I think their control is more hard than clothes dryer.

3. “Basically because given that the refrigerant temperature equates to pressure of refrigerant you might imagine that some serious pressures are normal. I don’t have a comparator with me but 400psig was common using R22. Compressors did not last.”
The air conditioner can last more than 10k hours. That is enough for a clothes dryer

[clever dicky]

Re: heat pump tumble dryer

Mate your not asking much. Not only are you asking to explain theory of refrigeration and knowledge but stuff you might never read from a book. Please read up on thermodynamics. (Heat)

But to explain briefly in ‘heatpump’ tumble dryer terms.

Think about the washing you would like to dry. How much does it way? Its this weight or mass you need to heat up – not air as an ac unit.

You need to heat the washing so the water evaporates (not all of it at once) but enough to get process started. Once water has turned to a vapour (wet air) it has gained some energy (heat). This then is atracted (for want of a simpler description) to anything colder (because it wants to turn back to a liquid, while at the same atmospheric pressure)
When it lands on the ‘colder’ evaporator coil it turns back to a liquid but in doing so gives up its energy (heat). This heat aids the adiabetic epansion of the refrigerant to also evaporate, the same way an ac system works. However a lot more heat (but QUANTITY not just TEMP) Imagine using your hair dryer even on a hot setting to dry your washing, it wouldnt be big enough right. Thats because of the qty of heat measured in jouls,watts, btu and so on. But this heat gets passed around the system and is got rid of from an already hot condenser coil, and is then used to continue heating up the washing even more. More heat – more water and so on.
Problems are caused not only by controling the whole process but by the mechanical damage. Much higher temps and pressure than any ac will ever deal with, and like your car look after it and it will last longer. Thrash or modify it to work on a race track and it will have more faults and wear out quicker.
Remember this. Only the theory and principles of refrigeration are the same. The application is completly different.

Hope

This is hHowever,

[kwatt]

Re: heat pump tumble dryer

Which is why I said that in a commercial situation this may be a go’r due to the economies of scale, but to try to impliment such a complex set of conditions in a box that’s 600x600x850mm and still allow the user to dry a reasonable amount of clothing is just not happening IMO with current technologies. Even in a dryer, which is pretty much empty bar a drum, heater and motor that are of any notable size, that’s a huge chunk of space eaten up already and then on top of that you have the venting or condensate collection facilities. There’s no way that I could envisage a condensor, evaporator and a compressor in there big enough to do the job and at the same time compete with the load size of a normal condensor dryer. I’m not saying it’s not possible, but highly improbable to meet market expectations on pricing and performance expectations as well.

Interesting idea though.

K.

[admin]

Hi: clever dicky

I think I know thermodynamics but still can’t catch your point.

1. There are no difference between narmal clothes dryer and heat pump clothes dryer to heat washing. It do need a lot of heat to heat washing first and then evaporate water but this happens in the traditional dryer too.

2. The heat pump dryer has to provide enough heat (QUANTITY you mentioned). I don’t know why you said this is a problem. AC provide those heat which can be far more.

3. You said “Much higher temps and pressure than any ac will ever deal with”. I do remember you mentioned a 90 C dryer chamber temperature. I think the clother dryer drum temperatrure is lower (I did measure a small commercial dryer chamber temperature and the max temperature is about 75C and the dryer stays in about 40C for most of time). The AC condenser design is very simple and it can get air to 50C. If you design the condenser for clothes dryer this air temperature can be high (above 80). So I don’t think in this condition machanical damage is not a big problem.

I will think this application is same as AC but need some fine design.

Hope you can point out what is wrong in my message.

[admin]

Hi: kwatt

I think we are talking about the heat pump clothes dryer which can decrease energy consumption 50{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} in current condition. Clearly there are some problems. One is high price and other one may be performance (i think) etc. There is no doubt that the size is problem too because you have to add several parts (like you mentioned).

When we talk some new things we can’t limit our eye to a small area. I never think the size is an issue which will kill this product.
1. If there is no other problem except size is too big the heat pump dryer will be a very good product, right? People who live in big house or have enough space to put this dryer will buy it. People who hasn’t space to hold this dryer will do some change in their space to try to install it. If they really have no space to put it they will not buy it. In the future the new house will have enough space (standard or optional).

2. I live in US and we have large laundry space. Many family in here have large laundry space to. IN the future many and many home can have a large laundry space if it is necessary.

[clever dicky]

Re: heat pump tumble dryer

Hi Guys, still strugleing? It is difficult to get your head around. The whole heatpump drying business blew me away and that was after years already working in refrigeration and college.
Something to bear in mind when comparing ac and heatpump dryers is they ARE the same refrigeration process. The transfer of thermall energy from one side to the other. That said, when you then make comparisons about temperatures close to .. or nearly … the applications are a world apart.

For a start on a basic or even highly complicated and complex ac system the whole point is that there is an ever increasing temperature difference between the cold (evaporator) side and the hot (condenser) side of a system. The cold side suction gas cools the compressor. Also there is a temperature difference between ambient (outside) air temperature and the condenser coil. Lots of oppertunity to get rid of that excess heat.

In a heatpump dryer its both coils need to be on the inside. The excess heat from the condenser is used to continue heating the load. Not only that, you are still ADDING heat to the same load to evaporate the water but also from the system itself. Think of a de-humidifier in a steam room, with extra heaters and a couple of fans blowing at it. But remember if the load that your drying gets to say 50’c, your evaporator is at the same temperature. And its from all the thermal energy of the water vapour, (from the energy of condensing water vapour) of the water condensing ( that makes the whole thing so efficient) but your suction gas is going to be pretty high at 50’c and so the refrigerant is at quite a high pressure already. There are many things that can be done to help, such as additional outside coils, but it is by its nature a cruel process.

I think its completly possible without doubt to scale the whole thing down to work and fit inside a large dryer, but parts would have to be first rate. Especially with the pressures, but I think its likely that the process would be adapted to not work quite like (and so with out all the bennefit) of a large commercial heatpump (dehumidifier). My feeling is that if one does appear it will more likly appear much like a normal ‘condenser’ dryer you get now, but with only an assisted cold side on the heat exchanger. Theres even the possibility of cycling cold water through a water cooled heat exchanger to below the dew point.

Hope this helps

[kwatt]

Re: heat pump tumble dryer

No Mazda609, in the US you guys have the luxury of space in most homes that we don’t in Western Europe, so we’re limited by size massively. Some of the kitchens we work in you actually do not have room to test a machine once it’s drawn out and the measurements given are for a standard Euro-box as kitchens here are almost universally standard sizes. I’d guess that well over 90{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} of washers, dryers and the vast majority of dishwashers were that size. The number of people that have space for a proper laundry room is low, although there is a market for larger appliances it is small.

However, before people here increased the size, or space allocated to laundry, they’d far rather have a large cooker or fridge I expect so the sales on a larger machine that was way more expensive would be extremely limited in Europe most likely. And, as Clever Dicky says, whilst you probably could scale the components down to make it fit there’s a lot of trade-offs to be made to achieve that which would likely make it impracticle at best to manufacture on any sort of scale.

Space in most of Europe is at a premium, very expensive and people here I think would much rather allocate any free space to other purposes.

K.

[dpm]

Hmm. I’ve read this thread, and what little I know of thermodynamics makes me agree with Clever Dicky.
I also wonder whether going for a full heat pump setup alone is indeed too complex, and slow to get up to temperature.

Maybe a *small* heating element is all that’s needed to improve matters, using the HP primarily for dehumidification?

Or even, what’s wrong with adding a Peltier device to any of todays condenser dryers, to improve the efficiency of the condenser?

[admin]

Re: heat pump tumble dryer

kwatt wrote:No Mazda609, in the US you guys have the luxury of space in most homes that we don’t in Western Europe, so we’re limited by size massively. Some of the kitchens we work in you actually do not have room to test a machine once it’s drawn out and the measurements given are for a standard Euro-box as kitchens here are almost universally standard sizes. I’d guess that well over 90{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} of washers, dryers and the vast majority of dishwashers were that size. The number of people that have space for a proper laundry room is low, although there is a market for larger appliances it is small.

However, before people here increased the size, or space allocated to laundry, they’d far rather have a large cooker or fridge I expect so the sales on a larger machine that was way more expensive would be extremely limited in Europe most likely. And, as Clever Dicky says, whilst you probably could scale the components down to make it fit there’s a lot of trade-offs to be made to achieve that which would likely make it impracticle at best to manufacture on any sort of scale.

Space in most of Europe is at a premium, very expensive and people here I think would much rather allocate any free space to other purposes.

K.

So you will think there is no problem for heat pump clothes dryer to be used in US, right?

[admin]

Re: heat pump tumble dryer

clever dicky wrote:Hi Guys, still strugleing? It is difficult to get your head around. The whole heatpump drying business blew me away and that was after years already working in refrigeration and college.
Something to bear in mind when comparing ac and heatpump dryers is they ARE the same refrigeration process. The transfer of thermall energy from one side to the other. That said, when you then make comparisons about temperatures close to .. or nearly … the applications are a world apart.

For a start on a basic or even highly complicated and complex ac system the whole point is that there is an ever increasing temperature difference between the cold (evaporator) side and the hot (condenser) side of a system. The cold side suction gas cools the compressor. Also there is a temperature difference between ambient (outside) air temperature and the condenser coil. Lots of oppertunity to get rid of that excess heat.

In a heatpump dryer its both coils need to be on the inside. The excess heat from the condenser is used to continue heating the load. Not only that, you are still ADDING heat to the same load to evaporate the water but also from the system itself. Think of a de-humidifier in a steam room, with extra heaters and a couple of fans blowing at it. But remember if the load that your drying gets to say 50’c, your evaporator is at the same temperature. And its from all the thermal energy of the water vapour, (from the energy of condensing water vapour) of the water condensing ( that makes the whole thing so efficient) but your suction gas is going to be pretty high at 50’c and so the refrigerant is at quite a high pressure already. There are many things that can be done to help, such as additional outside coils, but it is by its nature a cruel process.

I think its completly possible without doubt to scale the whole thing down to work and fit inside a large dryer, but parts would have to be first rate. Especially with the pressures, but I think its likely that the process would be adapted to not work quite like (and so with out all the bennefit) of a large commercial heatpump (dehumidifier). My feeling is that if one does appear it will more likly appear much like a normal ‘condenser’ dryer you get now, but with only an assisted cold side on the heat exchanger. Theres even the possibility of cycling cold water through a water cooled heat exchanger to below the dew point.

Hope this helps

I am really feeling bad to understand your points. I may need to learn more theromodynamics.

We are discussing a new product which clearly has big advantage and disadvantage. The important thing we should remember is that we are not limited in current design. As I said in my previous post there are some serious problems in current design and those problems are true problems you just mentioned in here.

1. Initialy the heat pump can’t get heat back from evaporated water. So in certain time period the COP of system is near 1 and this also means it will take longer time to finish all drying process. I will think this is also the problem why heat pump clothes dryer only can decrease energy cost 50{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d},
Can this problem be solved? Sure it can and my main idea is to solve this problem (sorry i can’t tell it in here).

2. If your drying is at 50C and your evaporate is at 50C too?
Again you make your point based on current design.
I will say it is not. At least in my design it is not.
Even it is in this condition we still can do some work in compressor such as decreasing compress ratio.

[kwatt]

Re: heat pump tumble dryer

mazda609 wrote:So you will think there is no problem for heat pump clothes dryer to be used in US, right?

Not entirely no, it would be easier as many US homes have a dedicated laundry area and condos/flats tend to offer communal laundry and drying facilities from what I’ve seen in the US. But even ignoring that there is still the price to benefit barrier to break.

But I do watch the US market and take note of it and it appears to me that there seems to be a shift away from the larger appliances and more towards the EU type of appliance. You can see evidence of this in some of the European manufacturers such as Bosch, ASKO, Fagor and others making a push for US sales. These newer (to the US market anyway) appliances are often regarded as “high-end, high-value” so whether the product is sustainable I really woudn’t care to guess.

I’m not so sure about dryers in different markets as I’ve not looked in any great depth into the subject, but from region to region or more approriately, continent to continent there are vast differences in how people wash and what they expect from a washer or a cooker so I should imagine that will carry through on dryers as well.

K.

[clever dicky]

Re: heat pump tumble dryer

I agree with some good points. Peltier on the heat exchanger I hadnt thought of and they’re starting to be more popular now with fridges too. A good market might be retrofitting existing condenser packs. Only needs to be colder than the dew point and be big enough for the load so an easy ‘upgrade’. Very power hungry, but very usful in hot humid areas.

Another thought, something I might try is swapping hoses temporarily on the washer to use hot water instead of cold. After thinking about this its obvious that ‘hot’ washing that goes into the dryer will give it a head start. Its a shame you cant prog the washer to give a final rinse in warm or hot water. I’ve a big water tank on the go all the time that only gets used to wash a few cups. Shower mostly, so might as well try it. Should increase drying time.

But got to say I feel its legislation that ‘controls’ or stifels innovation and competition.
Certainly manufacturers could do a lot better than they do but only do the minimum to stay in front of legislation knowing thats all their rivals will do.

[kwatt]

Clever Dicky,

Hot fill = a waste of time! 😉

In most modern machine once the cold water is transferred from the pipework to the machine it’s full. You just filled the pipes with nice hot water that’s been wasted.

It’s also cheaper to heat the water using the heater than to use a combi boiler, from memory it costs less to do a 40oC wash than to boil a typical kettle.

K.

[clever dicky]

Re: heat pump tumble dryer

Well it was just a thought. Wouldnt be wasting anymore than already. It only sits in the tank waiting to bve used anyway. I want the washing to come out warmer so it ‘should’ reduce heating needed straight away / increase water condensing rate .

Anyway just found a couple of links might be interesting.

The bottom one is more of the sort of heatpumpdryer that I remember:-

http://www.nyletherm.com/dryer.htm

http://www.eng.nus.edu.sg/EResnews/9902/p2.html

[kwatt]

Re: heat pump tumble dryer

I doubt it would make a huge difference, heat loss on the spin then transfer to another cold drum, then heat loss as the dryer heats up. probably not worth the hassle. Apart from which you run the risk of damaging more delicate items due to the high temperature of the incoming water, if it gets that high, but I have seen it happen when people instasll them wrongly as I’m sure many of the guys here have. Yet another tale that says, “READ THE MANUAL!”

Anyway, on the Nyle machine I can’t find a price but I’m betting it ain’t gonna be cheap.

The savings have no load reference on them, as in they do not offer the typical loads and time in operation to accomplish the saving mentioned. In other words it marketing gobble-de-gook that doesn’t say anything other than what people want to hear unless they actually look closely.

The other one’s a bit big for my kitchen. 😉

K.

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