Heat Pump Dryer Explained

Historically, having a washer and a dryer in your house requires “a hookup.” You need hot and cold water for the washer as well as a drain for wastewater. For the dryer, you need either gas or — in the US — a special 220 V outlet because the heating elements require a lot of wattage, and doubling the voltage keeps the current levels manageable. You also need a bulky hose to vent hot moist air out of the house. But a relatively new technology is changing that. Instead of using a heater, these new dryers use a heat pump, and [Matt Ferrell] shows us his dryer and discusses the pros and cons in a video you can below. We liked it because it did get into a bit of detail about the principle of operation.

These dryers are attractive because they use less power and don’t require gas or a 220 V outlet. They also don’t need a vent hose which means they can sit much closer to the wall and take up less space. Heat pumps don’t convert electrical energy into heat like a normal heating element. Instead, it uses a compressor to move heat from one place to another. In this case, the dryer heats the air using the heat pump. That causes water in the clothes to evaporate into the air. The heat pump dryer then uses a second loop to cool the air, condensing the water out so the it can reheat the air and start the whole cycle over again.

Where does the water go? Depends. Most models have a tank that fills up, and you can empty it every few loads. However, most dryers can also drain water directly down the same drain your washing machine uses.

[Matt] reports that the clothes don’t always seem very dry at the end of the cycle, which matches our experience with these dryers. However, some of this is just perception. If the clothes air out briefly, they are dry — the dryer drum is just moister than what you used to.

We’ve used these dryers. If you don’t mind the smaller typical size and want a neater installation, this is a reasonable answer. If you want cheaper operating costs, they are definitely worth a look.

Of course, a heat pump can warm you up, too. If heat pumps aren’t exotic enough for you, try drying your clothes with ultrasonics.

98 thoughts on “Heat Pump Dryer Explained

    1. So I heat pump dryer seems to be about $800 versus a traditional dryer that starts out at about 5 or 600. However heat pump dryers caused about 15 cents less per load to draw your clothes so in a traditional house like mine where we use the dryer every single day that would be about 50 to $75 per year minimum worth saving and it would pay itself back in about five or six years besides the fact and if you have a new house you don’t need a 220 line which is a big savings also. But I’m sure other people will have other ideas

    1. Almost 2024, and USA discover HP systems use for something else than home and car cooling 😉 it has been the norm for quite some time in Europe.

      Clothes driers damage fabric no matter the technology, in my house, we use traditional air drying/hanging in a small utility room, but assisted by very compact air dehumidifier (heat pump). Sure it doesn’t dry in only 1h (more a night) but you can hang as many you like there!

      1. I live in Australia, and hanging your clothes outside to dry also damages them, significantly fading them to the point that if you’ll have stripes all over your tshirts where they’ve been hung over a clothes line. Even turning them inside out doesn’t really help, it just makes the UV damage uniform.

        I guess the point I’m making is: don’t be so quick to dismiss a technological solution to a problem just because it doesn’t suit *your* scenario.

    1. You’ve got it backwards. You’re already effectively forced to use whatever fuel was used to make the electricity to spin the drum – plus whatever fuel is used to generate the heat – unless you generate your own power. If you’ve got a more efficient dryer, you’ve got less load to handle to become grid independent.

      Right now it’s 25F outside, but my entire poorly-insulated 1960s house is at 70-72F using air-to-air heat pumps running on electricity I made myself from solar. My hot water heater is a hybrid heat pump / electric that can keep up with two showers running at once with no problem, and dehumidifies my basement. The cold air exhausts into the basement, which isn’t ideal in winter except… I warm that air back up with the mini-split heat pumps I heat the rest of the house with. Oh, and the extra power I generate? The power company sends me a check instead of the other way around :)

      I went for a pretty big setup for my solar – over 15kw installed in panels to make sure I could handle that kind of load – but not everybody has the luxury of slapping that big a solar array on their house. Smaller power draw for long-running loads = smaller array needed. That’s where these dryers come in.

      1. If I wanted to be grid independent I would hang up my clothes outside. Not really an option in the winter where I am.

        Your best bet is to upgrade insulation. You may be able to get blown-in type that is easier to install. Better upgrade than solar.

        1. I did get insulation and did major house sealing as well – that was only a couple thousand dollars in all. However, the house still has single pane windows and upgrading those would cost quite a bit, and wouldn’t also cover my electric bill. I live in a place where a cold snap dropped it to -9F last year, and that’s not even a bad one. The cost of the panels minus the rebates was about the same, and I got a new roof in the process.

          This house was built during a time of falling oil prices, and so the solution to cold weather was to put in normal amounts of attic insulation, nice-looking but thin single pane windows, and then stuff a giant oil furnace and hot water heater in there to keep the thing warm. I’ve replaced the oil with heat pumps and upgraded the insulation, but otherwise? Working as intended ;)

          Like, you don’t have to be a green energy nerd for it to be pretty helpful. Even your example of hanging your clothes up outside. I just… use my electric dryer. I make lots of electricity, so it’s fine. If I had a heat pump one, or a hybrid heat pump electric one (which they already make) it’d just be more money in my pocket.

          Keep in mind I get more benefit than just keeping my house the right temperature. My battery backup will mean my house stands a good chance of only needing to PUSH power to the grid instead of pull for the next couple decades. The power company also pays for the electricity – first check this week! Around $60, even though it’s fall/winter! When the batteries are in there’s a program to pull from them during demand, and in the summer that pays $200/KW they pull. They’ll do 30-60 of those pulls a year. I’m literally gonna be a powerplant.

          As an aside, much like my hybrid hot water tank which still has regular heating elements, they also make larger hybrid heat pump / electric dryers that appear to overcome all of the limitations expressed in the video while still being ventless. A quick search of “Hybrid Heat Pump Dryer” yields quite a few results from a variety of brands.

        2. You’re assuming people installing solar haven’t already done insulation improvements, or don’t do them at the same time. There are substantial rebates available in my area for insulation work – it’s practically free.

          Everyone I know who has installed solar undertook some energy efficiency audits at the same time.

          Your petulance at efforts to slow climate change are boorish, selfish, and ignorant.

        1. It’s a Premier Hybrid! HPX-50-DHPTNE. It really is awesome! I will say, there are some caveats!

          It’s basically an indoor air conditioner with the hot side pushed into your hot water tank. You need to account for the new slightly louder noise from your utility room, and new ventilation if it’s enclosed – louvered doors, or they make duct kits. I have a duct to the input and a grate near the floor to dump cold air out of the utility room. You also need a condensate drain. Mine is via a condensate pump up and out through the outside wall.

          If the noise bugs you it’s easy to switch it to electric mode for up to two days and it’ll work like a standard hot water tank again. You lose some of the capacity, but otherwise fine. As a bit of idiot-proofing it’ll automatically reset to hybrid after those two days. However, if you’re trying to set it to regular electric mode for longer (something breaks, it’s already too dry in your house, your heat is busted and you don’t want an indoor air conditioner) I’ve seen youtube videos that show how to disable the auto-reset on similar models.

      2. Good points, but poster was kidding about mandates, which aren’t real but should be. Fortunately modern dryers are such crap that they need to be replaced every 4 years. Perfect time for an environmental upgrade.

        1. Whenever the title post contains certain keywords now, these political trolls show up to provoke. Never see them on the other articles tho.

          Almost like they’re using Google alerts, or not scripts.

    2. Fear monger somewhere else.

      P.S. it still uses electricity, just less than a standard electric dryer. LED bulbs are probably the only time in history that we’ve been forced to use the more efficient option.

    3. No, you can dry on a line like the rest if you can’t afford a heat pump. We don’t need to obtain your consent because you haven’t obtained all of our consent to breathe your poisonous fumes.

    1. LG sold them in the US since 2005 or so. Uses about 1/3 the energy of a regular electric dryer per load, I/m sure newer ones are even better.

      That said, it would be interesting to find out how much efficiency can be gained on a regular gas or electric dryer just by adding a heat recovery heat exchanger. I have a clue it would give a substantial improvement for a low cost, and therefore should be required for new dryers.

  1. I’ve been using heat pump dryers for about two years now.

    They are a miracle. I could never go back to a horrible, energy sucking, fire-risk inducing, clothes destroying vented dryer (we have 240V by default, so that issue isn’t a problem here).

    But if your clothes are coming out wet, then you’ve set up the dryer wrong. Increase the drying level, or follow the manufacturer’s rules for load (it’s amazing how many people overload both then complain “it doesn’t work”).

    They’re kind a like induction cooktops: most people who dislike them haven’t actually used them, or are running some mindless culture war. They’re simply far superior technology.

    1. I considered a heat-pump drier three years ago, but opted for an electric condensing one instead. The key factor at the time was the cycle time: heat pump systems are slower, and with three young kids in the house (one still in diapers at the time) I didn’t think a heat-pump would keep up with the pace of our washing.

      I have since been recommending heat-pump driers though: a single friend buying a flat is seriously considering one. They won’t need the quicker operation of a big condensing one, and the higher purchase price will soon be offset by the low running costs in today’s utility bills.

    1. Condensing dryers are different, I think they use a resistive heating element to heat the load and a cold water line to condense water from the load. When the cold water gets warm it gets dumped out. They’re much less efficient than a heat pump dryer but they’re cheap.

  2. We own such a dryer, and our electricity bill thanks us : it sucks 5 times less energy for the same job. So even if those are more expensive when you buy it, it’s worth it.
    Moreover (in France at least), you can find a broken one for cheap (usually they are sold as “broken” because of the door latch which is broken, or due to the electronic controller board which has died). Hence, it’s a cheap source of heat pump for mad projects we all have in mind :)
    I bought one for 30€, I recovered the heat pump only to make and air conditioner for my caravan (a 1974 Eriba Puck), and in the summer I can get a 30°C inside when it’s 40°C outside. The whole project costed me 100€.

  3. I use a piece of wire for this. First you mount the wire horizontally between two fixed points, then you put wet clothes over it and by some kind of magic they become dry after a while and you can take your clothes off again, or you just let them hang on the wire until you need them to cover body parts.

    You can also use multiple parallel wires to increase space efficiency. If you then put for example all the T-shirts on the same wire, it is easy to stack the dry shirts on top of each other if you need to make room for more wet shirts.

    1. in some climates, forget about that. we have a drier not because we are energy pigs, but because hanging outside can take weeks to dry. hanging them inside will make your apartment look green…

  4. quite common in europe since quite some time.
    i am not 100% convinced about saving power. i used to have a “conventional” dryer and it would dry clothes in half hour. the HP based one takes more like 2 hours. it uses less power but for longer.
    plus, tumbling clothes for 2 hours instead of 30 mins will quadruple the wear. yes, clothes wear out in the tumbler.
    they are also a lot more complex and prone to failure. or misuse from the missus. common cause of failure is the condenser completely blocked by lint due to failure of filters. some units require complete disassembly to clean the condenser radiator with a pressure washer, ask me how i know. most of the plastic tabs that keep them together will break. not really designed to be serviced.

    1. There’s a tradeoff with power and speed. Heat pumps become less “efficient” the greater the temperature difference they’re trying to create, so making the drum hotter to increase evaporation, and making the condenser colder to speed water take-up, will make the heat pump use more energy.

      If it runs at a very small temperature difference, it has to run forever to dry the clothes. If it runs as quickly as a normal dryer, it takes almost as much power. A compromise in between may take four times longer but uses 1/8th the power, saving you half the total energy.

  5. Is there anywhere in the US that (still) uses 220 V? It’s 240 V anywhere I’ve seen. Unless it’s 208 V three-phase, like many small commercial facilities and some apartment blocks. Is “220 V” just shorthand for “maybe 240 V, maybe 208 V”?

    1. US electricity is nominally 120/240 but of course there is some margin of error. If you’re close to a distribution point you might see as high as 125/250 and at the end of a line it can dip to 110/220. Some people prefer to talk in terms of the minimum but it can be misleading.

  6. I have a “clothes horse” that’s mounted above a radiator (gas fired central heating) and my clothes are dry in a few hours. I don’t have an external clothes line or a tumble drier. Been doing this for 25+ years and haven’t got a clue what everyone is on about.

    1. Over 30 years ago, I bought folding clothes drying rack at a yard sale for 50 cents. It paid for itself the first weekend by not needing to use the commercial dryer in the apartment complex. Although a dozen years ago (or so), I had to replace on of the wooden dowels that had broken.
      I haven’t amortized the cost of that repair.

    2. I’ve got a floor standing one, and my clothes are dry by the time I have to take them off for next week’s washing, so I’m in the same situation as you. I think part of the issue is that I only need to do one load of washing a week though, my friends with kids are basically *always* doing more washing.

    3. You haven’t a clue what people are on about? Many people live in places where you can spend most of the year waiting for the ambient humidity or temperature to be low enough to dry clothes indoors like that.

  7. One problem that never seems to get mentioned with heat pump water heaters and dryers is that they both take heat from the space they are located in. Typically that means the home heating system has to make up the heat used to heat water or dry clothes. Pay me now or pay me later, thermodynamics is ambivalent where your energy comes from.

    1. This is incorrect for heat pump dryers – both the evaporator and the condenser are inside the unit, so no heat leaves the system (a small amount of heat is actually added from the friction of the work being done by the compressor).

    2. Some homes, including mine, have the water heater in an un-conditioned space. My basement is below ground and not heated or cooled by my HVAC. It gets cold down there in winter but never freezing. A heat pump water heater in there would basically be an indirect geothermal setup.

      Even if what you said was true that would only mean heat pumps are no better than electric in winter but still an improvement in summer.

      1. If you were to pump the heat out of your basement, it would probably become freezing, and pull heat in from the house above.

        Geothermal energy is actually a misnomer. It’s heat from the sun that gets trapped in the ground. The actual heat from the earth’s core is a thousand times less.

        If you pull heat from right underneath your house, it’s basically being shadowed by the building and the ground becomes cold very quickly. That is why geothermal collection pipes are either spread around all over the yard in a trench just below the frost line, or drilled up to 200 meters straight down to increase the volume of soil you’re pulling the heat from. Still, deep geothermal wells eventually run cold and it takes 40-50 years to recover.

        1. Now that is an interesting assertion that geothermal is actually from solar and not from the earth’s core heat. I don’t find on DOE’s website where they address this:
          For household systems i.e., shalow sytems) they do seem to differentiate between trench horizontal systems (4 to 6 feet deep) versus deep vertical ones ( 100 to400 feet deep)

          “Shallow ground temperatures are relatively constant throughout the United States, so geothermal heat pumps (GHPs) can be effectively used almost anywhere.”

          “The ground heat exchanger in a GHP system is made up of a closed or open loop pipe system. Most common is the closed loop, in which high density polyethylene pipe is buried horizontally at 4 to 6 feet deep or vertically at 100 to 400 feet deep.”

          1. Shallow geothermal and groundwater approximate the local yearly average temperature. That’s just from all the thermal mass and poor conductivity. For this sort of heat pump, it can work but you do need to give the heat enough ground to slowly conduct into, especially if you don’t need the same amount of cooling in the year as heating, so that you’ve got to rob nearby ground to make up the difference. (Unless you make a point to make up the difference by exchanging with outside air and such when needed, because then your ground can just be a thermal mass again.)

            It’s only the *really* deep stuff where the temperature rises with depth, other than in places where hot springs exist.

    3. You are speaking of unducted unitary HPWH. You can duct them to the outside (although not in very cold climates), or even put them in the garage. There are also split HPWH where the compressor lives outdoors and the tank indoors. These perform favorably compared to even the highest rated unducted unitary HPWH installations because of the free heat.

  8. During the winter a dryer is 1/4 of the home furnace heat output. Now it’s going outside and that much cold air has to come in. They call it double indemnity. This convenient way of doing this has to go. I see current apartments going up and the walls are studded with dryer vents.

  9. Sir isn’t freezing clothes often a quick way to remove excess amounts of water? I have no experience with heatpump- dryers. But frozen clothes , yes. And though I still dry them, freezing first often means a few whacks with a broom side or small shovel makes the drying that much quicker( as long as there’s no rush, that is).

  10. Did I miss something? Did the laws of thermodynamics get re-written?

    It is impossible for this to use less power to do the same work. Whatever cool air this thing generates requires that the heating source of the home has to make it up. What is the thermal cost of these indoor heat pump systems? There is another energy source at play here. There must be. For that water to be exorcised from the fabric requires energy X. Now what magic does this tiny dryer use to make energy X? The answer is IT DOESN’T.

    My house will have to make up for the heat it generates. Once you determine what the energy required to make up that amount of heat you will then have the overall cost of running that appliance. While it may be lower than the electric model, I highly suspect it would not be nearly the difference they advertise.

    I have a 2 stage scroll compressor heatpump on my home paired with a variable speed fan system. It’s been working great. I have no complaints. I know the technology has some merit. But unless that generated cold side of the heat pump is piped outside in the winter it’s costing as much or more than the electric dryer it is meant to replace. In the summer you may see those good numbers, but not in the winter.

    I have often thought that the promise of heat pump technology is being mismanaged. Imagine a heat pump system that is built to have heating/cooling loops in the design that can be used for hot water, pool heating, and the like. Having valves to use that heating or cooling as the consumer wants. An in house co-generation of sorts. That’s how you make heat pump technology into the must have thermal control system of the future. Geothermal units can do it in some respects, but I would like to see the thermal transfer material be a simple liquid (likely glycol) that would allow deployment of the heat or cooling mass to wherever a homeowner requires it. Maybe even make it smart switchable to the sides. That way no matter what mode the heat pump is in for primary home comfort the nodes would either cool or heat with simple valve changes.

    In any case, Europe can keep this vaporware technology. I’ll stick with my easy to fix, fully operational after 20 years, electric dryer.

    1. Heat of evaporation is the same as heat of condensation – conservation of energy. You get the heat back on the cold side of the pump when the vapor turns to liquid again, so the pump pushes the same heat back into the drum, plus whatever power is used to drive the pump and turn the drum.

      Thermodynamically speaking, moving water from one container (your clothes) to a second container (the drain) takes no energy at all if the water remains liquid at the same temperature. If things were perfect, it would take no more than lifting a jug of water and pouring it down the sink. The fact that you lose heat or generate unnecessary extra heat at various points in the process is all that really consumes power.

      1. Re: the second paragraph, *in theory* you could even use a membrane and an air compressor to dry the air although it doesn’t sound like a good home appliance.

        There’s membrane separators that allow water to escape from compressed air, with minimal air pressure drop across the device and minimal leakage flow to blow the moisture away from the outside of the membrane. The *necessary* work should be mostly to drive the water thru a restriction by a difference in pressures, which is not bad since humid air is still mostly air.

        Normally this is where you’d use the compressed air to power a tool or let it escape through a restriction such as a blow nozzle, which accounts for the remaining energy. But if you have most of the volume and most of the pressure left, and especially if you have any way to arrange things so that some of your waste heat actually increases the pressure, then you could expand it the same way you compressed it, recovering a lot of the energy. Maybe you have a separate piston, delayed a number of degrees, with the membrane between the two, or something like that.

        Is it any good? Well, no-one’s doing it, and it’d be hard to get someone to start, and it probably still isn’t for clothes dryers. But membranes are still neat for simplifying problems where thermodynamics says it’s fine for something to move, but you have to figure out how to do it. Osmosis, ion exchanges, air separation, etc.

    2. Before you smugly assert that common appliances don’t work, try figuring out why people say they do.

      The water that condenses, as well as the air that carries it, returns energy to the system. It’s not pulling it out of the house, it’s pulling it out of its own exhaust and sending it back into its intake and adding in the majority of the electrical wattage it consumed. So there’s a loop where in one segment, heat is carried by refrigerant, but in the other segment, it’s carried in large part by the water that evaporates from the clothes and condenses elsewhere. Since there’s more circulating heat in the loop than the instantaneous electrical input, and the clothes are part of the loop, the electrical input can be smaller than normal for the same amount of evaporated water. I suppose once there’s not much water left, it’ll be mostly air carrying the heat, and maybe the water removal won’t be as good depending on the max temperature. But it’s fairly dry at that point, and anyway that sort of lower temperature drying isn’t exactly unheard of.

      There will still be waste heat, of course, and without anywhere else to go it will get dumped into the area around the appliance. Maybe a little can leave if the water going down the drain is fairly warm.
      But anyway, without a vent for the waste heat, this is actually best in winter and worst in summer.

      It may even be worse in terms of air conditioning load than a regular vented dryer in summer, unless the typical vent has enough airflow that the replacement air coming into the house from the hot outdoors represents more energy than the waste heat of this system. I don’t remember the numbers.

      1. What? You’re describing perpetual energy.

        “The water that condenses, as well as the air that carries it, returns energy to the system. It’s not pulling it out of the house, it’s pulling it out of its own exhaust and sending it back into its intake and adding in the majority of the electrical wattage it consumed.”

        1. No, I’m not. Any electrical air conditioner or heat pump demonstrates how the amount of heat exhausted from the hot side is limited to the electricity you put in PLUS the amount of heat energy that was pulled into the cold side. That means there’s more heat flowing out of the hot side than the amount of electricity you’re putting in. That’s entirely in keeping with the thermodynamic concept of what refrigeration even is.

          If you allow the exhaust heat to take a detour through some wet clothes, then the exhaust heat will be carried by warm moist air rather than hot dry air, but it’ll still exist and be flowing.

          If you pretend the device has one exhaust output where it’s got the chilled air and another one that’s got the warm moist exhaust, so that they mix and subtract out, and you’re left with the heat from electricity, does that help? Or are you just trolling?

  11. Got one of those combo units a few years back, paid an absolute mint for the privilege and it was one of the worst purchases i ever made. It would take 7 hours to dry a load of washing and would randomly decide that it was finished regardless of how wet the clothes were. Forget about towels. Had to do 4 warranty claims and each time they had to replace parts, I would have kept doing warranty claims except the warranty period had expired and it was cheaper to get a $300 dryer that works quickly and consistently.
    The technology might be solid but the implementation in modern appliances makes it less reliable then older technology.

    1. It might also have been paired with an inappropriate washer. Models vary on how much moisture is left, and an older/cheaper washer could have a high “remaining moisture content.”

  12. I want to think it’s installed the same way an a/c unit is, with the compressor and condenser outside instead of being a single unit. Otherwise it takes the heat from the inside air cooling it… bad business when it’s winter.

    1. If you do that, you’ll have to vent the moist air outdoors like a normal dryer, and then you’ll be making the temperature indoors worse than you would if you had just let it take the heat from its own exhaust instead. In fact, if it’s at a lower temperature, then the same amount of clothes will require even more exhaust air and therefore even more outside air leaking in to replace the air you exhausted.

      When you let it work the way it’s designed, the heat that goes into the cold side is supplied by the hot side, and it generates a certain amount of waste heat besides. That waste heat is actually why I don’t want one; the conventional dryer consumes more power but most of it goes out the exhaust instead of into the room in the summertime, and there’s probably less of that since it can use hotter air with less humidity as far as I know.

  13. I don’t know why everybody turns this into a big mysterious heat pump technical triumph. It’s just using the standard method of dehumidifying air to dry the clothes:
    1.) Blow near room temperature dry air through the tumbling clothes.
    2.) Run the now damp air through the lint filter to clean it.
    3.) Run the damp air across the cold coil of the “heat pump” to condense out the water.
    4.) Run the now cold dry air across the hot coil of the “heat pump” to bring it back up to near room temperature.
    5.) GOTO 1

    Just like your standard home dehumidifier, it just runs the air across a cold coil to condense moisture and then it runs that air across the hot coil to bring it back to its original temperature. It’s a closed system so the only addition heat comes from the inefficiencies of the motors and electronics. No air is brought in or exhausted. Of course they throw in some good engineering.

    1. That order of operations would make me expect this setup is giving the clothes *warm* dry air not ambient dry air, because the setup should be unlike and not equivalent to just having a dehumidifier in the room with the clothes hung up. All the water has to be condensed either way, but it should help that you’re driving it out of the clothes with heat to hopefully carry and condense more water for each volume of unnecessarily heated and cooled air in the cycle. Hmm, maybe a bit of reduced air pressure would help… :D

      1. Once the door is closed there is no way for additional air or heat to come into the system except for minor inefficiencies. Take a look at a teardown of this washer/dryer: it’s just dehumidifying the air, not adding additional heat. It does have a large fan to help blow the moisture out of the clothes.

        Creating a vacuum would be interesting.

        1. There’s a big way for energy to enter and turn into heat, it’s the motor of the pump. There should be a need for a bit of heat and some air circulation inside the chamber, so as to carry the most water per the amount of inert air that needs to be heated and cooled alongside it. The circulation to get high approaching maximum relative humidity, the heat in order to raise the bar for what the carrying capacity of the air actually is. Of course, still have to be in range for the best operating point of the heat pump and such, but hey.

          1. Again; take a look at the teardown. The path of the air is a closed system. All of the motors are outside of that closed system. Compressor, fan, drum and water pump motors are outside of that system. It simply dehumidifies the air and blows it through the clothes. The condenser and evaporator are both in the sealed airflow. It uses a large dehumidification system and a large fan to make all that work in a reasonable time.

            There is no significant heat added to that closed system.

          2. Again, that’s not the point. Even a physically ideal theoretical carnot refrigerator still requires an input of work. That work itself, plus the energy that is taken out of the cold side, appears as heat on the hot side. The thermodynamic cycle is completed by the refrigerant, so the relevant heat inputs and outputs to me are the evaporator and condenser in this case.

            Does that mean it gets particularly hot in there? No, I don’t doubt that if someone’s observed a particular place was no more than a bit warm, they were correct in their measurement. A home refrigerator’s hot side may be no more than slightly warmer than ambient, if it’s got good airflow and plenty of surface area. But it does mean there is an obvious and necessary energy input, and any proof to the contrary is a proof of having achieved overunity / free energy. You’d have beaten the carnot limit if you found a way to avoid any energy input to pump heat uphill across even a shallow temperature difference.

  14. We purchased a heatpump dryer a few years back and had the issue of it not drying the clothes properly until I noticed that it was saying it was finished based on the dryness setting. I found that I could bypass the sensors by adjusting the drying time and ignoring the preset modes. Now we get dry clothes when we don’t use the clothes line and I have a nice supply of distilled water for the clothes iron, car radiator or other experiments.

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