We do not know how clouds evolve. They may coagulate if they collide at velocities below the internal sound speed of a cloud. They may break apart in falling relative to the hot phase and then mix into it, which has the effect of causing the cooling time of the newly mixed gas to be reduced and so promote formation of a new rapidly cooling cloud. In the center of the flow, cloud-cloud collisions may be common since the density of clouds will be highest there. Despite these many uncertainties, we can identify some of the many stages in the cooling of a cloud.
Smaller clouds lose pressure equilibrium at lower temperatures.
It therefore becomes very short as the gas cools. Observations of the same value spectral from different X-ray lines characteristic of different temperatures give good evidence that flows are steady. The mass of gas expected in a cooling flow as a function of temperature should roughly resemble the inverse of the cooling function, i.e. where the cooling is strong and the cooling times short, there is little gas. The core quickly drops to the temperature of the microwave background. The mass can then be in the range of M crit 10-100 M , and perhaps more if the magnetic field came into equipartition with the thermal pressure at a much higher temperature.