In managing a large building (hotel, hospital, gym), the two biggest drains on the energy budget in summer are: Paying for electricity to cool the spaces, and simultaneously burning gas or electricity to heat water (DHW) for showers and pools.
What if we could "capture" the heat that the chiller uselessly throws into the environment and use it for free hot water? That is precisely the job of Heat Recovery Chillers.
This is the most popular application. When the refrigerant gas exits the compressor, it is extremely hot (80°C–90°C). This state is called "superheated gas". In a chiller with partial recovery, engineers insert a small heat exchanger - the Desuperheater - immediately after the compressor.
The hot refrigerant (80°C) passes through the Desuperheater. Simultaneously, cold mains water (e.g. 15°C) passes through the opposite circuit. The refrigerant transfers its "extreme" heat to the water. Result: hot water at 50°C–60°C, ready for showers.
Partial recovery captures approximately 15%–20% of the total rejected heat. It also slightly improves the chiller's own efficiency by helping it shed the difficult, initial superheat before reaching the condenser.
What if we want to exploit all the rejected heat? Total heat recovery chillers feature a second, parallel water-cooled condenser. Instead of dumping heat into the air via fans, the machine closes the valve to the fans and routes ALL the hot refrigerant through the water heat exchanger.
100% of the rejected heat is recovered. The water produced is "warm-hot" (~40°C–45°C). Ideal for hotels with heated pools or SPA centres - the chiller cools the rooms while simultaneously maintaining the large pool at 28°C for free.
Every summer, the chiller runs at 100% to cool the rooms. Instead of dumping ALL that heat into the air, the Desuperheater (or total recovery unit) sends it to the boilers. Result: the gas boiler stays off for 3–4 months per year, saving thousands of euros in gas or heating oil. In a typical 100-room hotel, this translates to savings that significantly exceed the component's purchase cost.
If it's so "magical", why don't we eliminate boilers entirely? To get free hot water, the building MUST be requesting cooling.
The chiller runs at 100%. The boilers overflow with free hot water. The gas boiler stays off, saving enormous amounts of energy.
The rooms don't turn on their ACs. The chiller is off. No rejected heat means no hot water produced at all. The primary source (heat pump or boiler) takes over completely.
Desuperheaters always operate as auxiliary systems. You still need a primary DHW source. But during the 3–4 hardest summer months, you save thousands of euros.
Adding a Desuperheater slightly increases the initial purchase cost of the machine, but in installations with high DHW demand (such as hotels and hospitals) the payback takes less than 2 summers. It is the very definition of circular, green engineering.
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