Here is the mistake this lesson exists to kill: a cooling tower does NOT reject the chiller's cooling load. It rejects the cooling load plus every kilowatt the compressor drew to move it, because that electricity also ends up as heat in the condenser. $Q_r = Q_e\,\mathrm{HRF}$ — Q-r equals Q-e times H R F. $Q_r$ is the heat rejection, in kilowatts, the number the tower is sized on; $Q_e$ is the evaporator load, in kilowatts, the number the building asked for; and $\mathrm{HRF}$ is the heat rejection factor, a bare multiplier that carries the compressor's own work.

HRF is about 1.25 for an electric chiller — the compressor adds roughly a quarter again — and about 1.8 for an absorption machine, which buys its work as heat and so throws far more of it away. It can never be below 1. A tower sized on the load alone is a quarter short, and it will discover that on the hottest afternoon of the year.

Then size the water that carries it: $\dot{V} = \dfrac{Q_r}{\rho c\,\Delta T}$, where $\dot{V}$ is the condenser water flow in litres per second, $\Delta T$ is the rise across the condenser in °C, and $\rho c$ is water's volumetric heat capacity, $4.18\ \mathrm{kJ}$ per litre per degree. Rearranged, that same constant is the trade's 500 rule wearing SI clothes.

The lore worth memorising: about 0.054 litres per second of condenser water per kilowatt of cooling — the metric face of the old three gallons per minute per ton at a ten-degree range. And note the lever in that denominator. Design for a WIDER range and the flow falls in proportion, taking pump power with it as the cube. That is the entire wide-delta-T argument, and it is worth more than most equipment upgrades.