Initially evaporation occurs, accelerated by the tidal effect, leading to gravothermal catastrophe. This is analogous to blowing up a balloon. The more molecules that are put in, the bigger it gets. Also, it depends on how fast the molecules are moving inside, which is related to the temperature. Heat is transferred from the water to the cooler air of balloon, causing the temperature of the balloon to rise.
Gravitational systems are peculiar in that smaller equals hotter.
Spacecraft in smaller orbits are always moving faster due to the stronger gravitational pull. For example, if you make a balloon smaller, the temperature goes up. Put the balloon into an ice bath, and it gets hotter because it shrinks. Globular clusters get smaller by removing stars. In shrinking, the temperature goes up, which leads to gravothermal catastrophe.