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Heat pumps of the 1800s are becoming the technology of the future

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Re: Heat pumps of the 1800s are becoming the technology of the future

#251

Post by twawaaay »

HellzStormer wrote: post #240
twawaaay wrote: post #231

I am in constant bewilderment about all of the talk of saving electricity but still so few homes having a very basic device like heat exchanger. At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box. Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep…

Logically (and ideally), the incoming air and outgoing air would exchange heat until they are at the same temp, which would be in the middle. So I would not expect an efficiency higher than 50% unless there is some special tech I'm not aware?

Imagine you have two very long tubes joined thermally throughout their entire lengths. For the sake of simplicity, no energy is exchanged with the environment, only between the two fluids.

The cold fluid will meet (thermally, in adjacent pipe) more and more hot other fluid and finally as it reaches the end it will meet the hot fluid at exactly the temperature it comes in. If the fluids are flowing slow enough and the thermal bond is good enough, the cold fluid can get heated up as close to the hot fluid temperature as you want.

And the hot fluid will meet colder and colder other fluid until it reaches the coldest at the other side.

The efficiency of heat exchanger could be as close to 100% as you want, in ideal world.

In real world higher efficiency requires larger device and there is a point of diminishing returns. You also get other losses like mechanical losses due to need to pump fluids through pipes (with large surface area), due to need to have turbulent flow (to ensure mixing within pipes) and due to heat loss to the environment.

Re: Heat pumps of the 1800s are becoming the technology of the future

#252

Post by [deleted] »

HellzStormer wrote: post #240
twawaaay wrote: post #231

I am in constant bewilderment about all of the talk of saving electricity but still so few homes having a very basic device like heat exchanger. At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box. Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep…

Logically (and ideally), the incoming air and outgoing air would exchange heat until they are at the same temp, which would be in the middle. So I would not expect an efficiency higher than 50% unless there is some special tech I'm not aware?

[deleted]

Re: Heat pumps of the 1800s are becoming the technology of the future

#253

Post by briHass »

ghettoCoder wrote: post #16
retrac wrote: post #10

Earlier quoted context omitted.

> it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed…

I always joke that in winter all appliances are 100% efficient (I know they're not). Some look at me funny but the ones who pay the gas bill get usually get it.

In the summer, my heat pump water heater in the basement is essentially 'free' to run, since most of the heat it captures is by condensing water in the air i.e. dehumidifying my basement. I still need a dehumidifier, but it doesn't have to run as hard.

Re: Heat pumps of the 1800s are becoming the technology of the future

#254

Post by darken »

twawaaay wrote: post #231

I am in constant bewilderment about all of the talk of saving electricity but still so few homes having a very basic device like heat exchanger. At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box. Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep…

We had one of these installed in the last couple of years and love it. We wanted to keep our CO2 lower, without leaving windows open and introducing dust/whatnot. Works well quantitatively and qualitatively.

FYI the "industry term" for these is an ERV or Energy Recovery Ventilator. (I think I've seen them referred to as Enthalpy Recovery Ventilator -- but I assume that fell out of favor since it's too pedantic for most people heh.)

If you get one, one tip is to ensure the air inlet is covered with a fine mesh screen. This cut the number in bugs in the filter 95%+. Also you can upgrade the filter from what's included to MERV13 or whatnot for better incoming air filtration.

Re: Heat pumps of the 1800s are becoming the technology of the future

#255

Post by goodpoint »

lll-o-lll wrote: post #192
phyzome wrote: post #144

> owners of drafty homes may need to take on the added cost of insulation when installing a heat pump Installing good insulation is also really important even if you're not using heat pumps! With bad insulation, you're wasting energy no matter what technology you're using.

If you live in a warm climate, I personally think insulation is the worst (excepting roofing). Not because of efficiency, but because you isolate yourself from nature! The traditional Queenslander (look up Bluey if you don’t know what I mean), has so much going for it. It allows airflow through the whole house, a protected outside to sit and be with nature, lizards coming and going, bliss! This hermetically sealed en…

> you isolate yourself from nature

That's a feature not a bug.

> This hermetically sealed environment that we create for ourselves is bad for us.

Not at all. Heat recovery vents exist for a reason!

Re: Heat pumps of the 1800s are becoming the technology of the future

#256

Post by darken »

HellzStormer wrote: post #240
twawaaay wrote: post #231

I am in constant bewilderment about all of the talk of saving electricity but still so few homes having a very basic device like heat exchanger. At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box. Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep…

Logically (and ideally), the incoming air and outgoing air would exchange heat until they are at the same temp, which would be in the middle. So I would not expect an efficiency higher than 50% unless there is some special tech I'm not aware?

According to Wikipedia, ERV (Energy Recovery Ventilators) can reach 90% efficiency via "modern low-cost gas-phase heat exchanger technology".

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

I think another part of this is that there is generally a significant moisture content difference between hot and cool air, leading to some additional gains versus thinking in terms of air temperature alone.

Re: Heat pumps of the 1800s are becoming the technology of the future

#257

Post by twawaaay »

darken wrote: post #254
twawaaay wrote: post #231

I am in constant bewilderment about all of the talk of saving electricity but still so few homes having a very basic device like heat exchanger. At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box. Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep…

We had one of these installed in the last couple of years and love it. We wanted to keep our CO2 lower, without leaving windows open and introducing dust/whatnot. Works well quantitatively and qualitatively. FYI the "industry term" for these is an ERV or Energy Recovery Ventilator. (I think I've seen them referred to as Enthalpy Recovery Ventilator -- but I assume that fell out of favor since it's too pedantic for mo…

I live in a large apartment (3 adults, 2 children to 1700 square feet). Recently I bought a good CO2 meter (Aranet4) and I really discovered how much you have to ventilate to keep CO2 levels under 1000ppm.

I sort of knew this for a long time and that's why I, for example, always sleep by an open window. But knowing it is one and actually seeing a completely different thing.

So this caused me to start thinking about installing one or more of these boxes in my apartment.

Re: Heat pumps of the 1800s are becoming the technology of the future

#258

Post by batiudrami »

jimmaswell wrote: post #238
fifteenforty wrote: post #159

Earlier quoted context omitted.

It’s a ‘mini split’ in US lingo. There are thin, highly insulated refrigerant lines going between the outside unit and the inside unit. The inside unit exchanges heat with the air. https://www.daikin.com.au/our-product-range/split-system-air...

That thing's an eyesore compared to a duct to me.

Much like solar panels on the roof (which I have also heard Americans describe as an eyesore), once they are common enough your eyes just slide over them and you don’t notice.

Re: Heat pumps of the 1800s are becoming the technology of the future

#259

Post by twawaaay »

darken wrote: post #256
HellzStormer wrote: post #240

Earlier quoted context omitted.

Logically (and ideally), the incoming air and outgoing air would exchange heat until they are at the same temp, which would be in the middle. So I would not expect an efficiency higher than 50% unless there is some special tech I'm not aware?

According to Wikipedia, ERV (Energy Recovery Ventilators) can reach 90% efficiency via "modern low-cost gas-phase heat exchanger technology". https://en.wikipedia.org/wiki/Energy_recovery_ventilation I think another part of this is that there is generally a significant moisture content difference between hot and cool air, leading to some additional gains versus thinking in terms of air temperature alone.

When cold air gets heated up the relative humidity gets lower. If you already have very cold winter which tends to be relatively dry -- you should add humidity and this will necessarily cool the air. While this is not strictly necessary, very dry air is not healthy or comfortable. You typically don't need to add humidity when the temperature outside is around freezing but air is very humid.

And conversely, if you live in very hot and humid climate, you need to remove water from incoming air (actually, there is no other way to cool the air). This unfortunately further warms the incoming air and will necessarily lower efficiency of the exchange. Especially because you don't want to remove only minimum humidity -- you probably want to remove enough of it to get to at least 70% for comfort.

So these are extreme climates. In a more moderate climate you can get away with no need to add or remove humidity and you can get as close to 100% efficiency as you want.

Re: Heat pumps of the 1800s are becoming the technology of the future

#260

Post by alvah »

nerdbert wrote: post #221
pinot wrote: post #168

Earlier quoted context omitted.

Can't heat with gas without electricity, unless you have a genset or power wall kind of thing to provide epower.

Until a couple years ago we had a gas-fired tankless water heater which used a single D-cell battery for ignition, which had to be changed once every year or two. It wasn't connected to wall power at all.

There are, or used to be, Bosch tankless water heaters which used a small turbine connected to a piezo-electric igniter, no external power source required ever.
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