Under the shell of the condenser we have multiple tubes inside. These run from one end to the other. Depending on the design the condenser water will either flow straight through all the tubes or it will flow in through half of them and then do a U turn and come back out the same end. This is to increase efficiency and reduce the size.
The tubes contain the condenser water. On the outside of the tubes is the refrigerant which is coming from the compressor. The two fluids are always separated by the tube wall. They’re completely isolated from each other.
The condenser water is coming from the cooling tower, into the condenser via the inlet on the “water box” (The end cover). The water box section is removable is taken off for cleaning of the tubes. The condenser water flows through the tubes to the very end, hits the other water box at the end, does a 180 degree turn, comes back through the tubes and back out the first water box.
There’s a baffle between the inlet and outlet on the first water box. This is just there to separate and divert the flow into the correct tubes.
Hot compressed refrigerant is going to come out of the compressor and start to fill this void within the condenser. The hot refrigerant vapour will fill the space between the tubes containing the condenser water.
As the hot refrigerant comes into contact with the cooler surface of the condenser tubes, the refrigerant is going to condense into a liquid on the tubes surface. As it does so the heat will transfer through the tube wall and into the refrigerant.
The condenser water runs through the condenser, hits the end water box, does a 180 degree turn and comes back through, still picking up the last heat it can to the maximum efficiency. Meanwhile the liquid refrigerant collects as a liquid at the bottom of the condenser. It will leave here through the bottom and flows into the expansion valve. The heated condenser water will now head off to the cooling tower.
When the refrigerant exits the compressor and heads down into the condenser, it needs to be at a much higher temperature than the return (incoming) condenser water that’s coming back from the cooling tower. The condenser water enters at around 27 ° C (81 ° F) so the refrigerant needs to be a greater temperature than this.
If the refrigerant is the same temperature as this return condenser water then the chiller will not be able to reject any heat that’s been picked up in the building, and so the building will be unable to cool down.
Equally if the cooling tower is unable to reject the heat that’s being sent up to it, then it’s going to return at the same temperature. E.g. if it’s going up at 32 degrees Celsius, and the cooling tower is unable to reject this heat, (perhaps there is recirculation happening or the water is just dumping instead of spraying, or there’s a problem with the baffles) and the water is just returning straight back down into the condenser, then you will not be able to reject any heat from the compressor and it will eventually cause the chiller to trip on high pressure.