Technology

There are three modes of heat transfer; conduction, convection, and radiation.

Conduction happens when two bodies at different temperatures come into contact with each other. The total heat transfer depends primarily on the difference in temperature, contact surface area and time spent in contact.

Convection takes place when a fluid (I.e. a gas such as air or a liquid such as water) comes into contact with another body. Here, again, heat transfer depends on difference in temperature, contact ("wetted") surface area and time in contact which is primarily dictated by how fast the fluid is moving over the body.

On Earth we generally leverage these two modes. An example of mixing the two modes is a CPU heatsink and fan setup. The heatsink conducts heat away from the CPU and is (usually) distributed throughout several extended surfaces I.e. fins. The fins increase the surface area in contact with air, enhancing the rate of heat transfer.

Now, we can't really take advantage of those in space. The lack of an independent physical medium means the heat ultimately has no where to go; this is known as a "closed system". So if we generate or store enough heat in a body subject to the void of space without promoting radiative heat transfer, that heat will more or less stay put.

Radiative heat transfer is fucked up. Everything above absolute zero radiates heat. You mostly can't see this except for one glaringly obvious example; the Sun. Sol is so fucking hot that it heats the Earth through the vacuum of space purely via anger aka photons. And thanks to the miracle of science, you radiate anger right back at it.

Explaining radiative heat transfer further is outside the scope of this reply and will be left as an exercise to the reader.

I hope I explained this well enough for you or other readers to impart a 'basic' idea of a complex engineering discipline that I adore. I'm absolutely willing to answer any questions.