Heat Pump

A heat pump is the opposite of a heat engine. Rather than obtaining useful work as heat flows "downhill" from hot to cold, a heat pump uses work as an input in order to pump heat "uphill" from cold to hot.

[@mcalkis5771]

In the case of heating, why is the heat q_h negative? Shouldn't it be positive since heat is gained by the system to heat it up?

[@shashidharsahu8272]

Hello sir big fan ,from india.plz sir complete physical spectroscopy the electronic spectroscopy portions and the rest humble request ur teaching is really outstanding..

[@PhysicalChemistry]

Sorry, I don't have any plans to make more spectroscopy videos. I hope you can find someone who does that course on KZbin

[@RichardKCollins]

Is a heat pump worthwhile? How does that convert into economics? If you are going to talk about thermodynamics, then what is going on in the air and in the heat pump that lets it do its job well? What is different about the air inside and outside? Where is the heat stored? What allows the "hot" to be identified and pumped? Why not pump "cold" molecules from hot air the same way? Maxwell Demon's were pretty clear and workable. All this nano technology, and laser Doppler spectroscopy, there can be a better way to heat and cool air. Heat and cool water. Heat and cool people. Heat and cool engines, reactors, sensors, power supplies, plasmas. Your magic board is cute. But I would rather see a computer screen with the equations neatly typed, and diagrams working as real parts of a calculator and simulator. I would like to see real data from heat pumps and the economic consequences of engineering and physical chemistry choices. I would like to see real measurements of real devices and microscopic and nanoscopic details of where the energy is going, what it looks like and how it can optimally be pumped. Get off the screen, you can prepare and then demonstrate and explain and guide. I like what you are doing, but I think you have a lot more to give to the Internet. You need to challenge yourself and remember there are 7.9 Billion people in the world, two billion "first time learners" from 5-21, and about 4.8 Billion with some current access to the Internet. Who is doing the "best in world" designs and methods for heat pumps? Could a rocket engine operate as a heat pump? Can you get a heat pump to resonate and lock in like a pumped laser? How do you measure the heat signature of the air coming to be separated? How do you pump molecules? (atom interferometer gravimeters do it). Where do people go to fundamentally change the way engineering design is done? Ask Elon Musk, he has an answer for everything. Keep up the great work! Richard Collins, The Internet Foundation

[@PhysicalChemistry]

Thanks, that's quite a collection of questions and comments! What's "going on" in air that lets us use its heat to do work is the kinetic energy of the molecules. This was developed in detail in several earlier videos in the sequence, including those in the kinetic theory of gases playlist: kzbin.info/www/bejne/onmzeaiYmquhrZI Likewise, the heat is stored in the kinetic energy of the molecules in the air. The only difference between the air inside and the air outside (the hot reservoir and the cold reservoir) is the temperature, and thus the distribution of kinetic energies. There is no Maxwell's Demon identifying the hot and cold molecules, and pumping them. That's the beauty of the second law of thermodynamics. When run as a heat engine, heat naturally flows from hot to cold without a need for Maxwell's Demon or anyone else to control the specific collisions. When run in reverse, as a heat pump, we can get heat to flow from cold to hot, but it costs us energy. The heating / cooling can be done by a variety of processes like PV work (compression / expansion). We just have to put more energy into the heating phase than we get back in the cooling phase. For specifics on data, and devices, and components, etc, you're better off looking at engineering sources. This video is focused on the thermodynamics of heat pumps. By studying ideal / theoretical heat pumps, we learn about universal truths that are always true, guaranteed by the laws of thermodynamics. You can consider these to be the upper bound for how well a real-world device could work. Then the details of constructing and optimizing real-world devices are much more work, and have consumed decades worth of iteration by an army of engineers.