Waste heat becomes a source of energy - Efficiency element no. 2: Heat recovery

Waste heat becomes a source of energy - Efficiency element no. 2: Heat recovery

Heat is an inevitable byproduct of every machine. In the case of vacuum pumps, it is generated by the motor, friction and, above all, the compression of gas on the discharge side. However, with the right measures, the heat can be used as a source of energy, which naturally increases the overall efficiency of the system. The benefit becomes even greater if the vacuum pump is used in a cooled environment, such as in the food industry. This reduces the demand on the air conditioning, as the installed vacuum pumps give off barely any waste heat.

Heat recovery levels of 50 to 70 percent possible

Even the most efficient vacuum pumps generate heat during operation. Normally, this heat is emitted into the environment without being used, where it then heats up the space around it. It is not only in cooled environments that this effect is undesirable. In temperature-controlled spaces, the released heat also has to be balanced out by air conditioning systems. This leads to an increased energy consumption and correspondingly higher energy costs.

Heat is energy: it makes economic and ecological sense to make use of it. Heat exchangers can make a significant contribution to reducing the total energy consumption in vacuum generation processes and decreasing their carbon footprint. They can be used to recover a large portion of the heat so that it can be used for room heating or hot water generation. The general rule of thumb is that heat recovery processes allow 50 to 70 percent of the energy consumed by the motor to be captured for other uses.

An air-cooled rotary vane vacuum pump with a pumping speed of 1000 m³/h, 4,000 operating hours per year and an operating pressure of 100 millibar emits approximately 17 kW/h of energy in the form of heat, which is released into the environment. An oil-water heat exchanger by Busch can recover up to 70 percent of the ingoing energy for further use. At energy costs of €0.18/kWh, this results in annual savings of up to 9,500 Euro and over 22 tonnes of CO2.

Heat exchanger technology

Busch offers a wide range of heat exchanger technologies for heat recovery. For instance, an oil-water heat exchanger is suitable for oil-lubricated vacuum pumps. The operating fluid (oil) heats up during compression. Its heat is transferred to a water circuit in the heat exchanger. Water-water heat exchangers are suitable for liquid ring vacuum pumps, among others. In this case, the heat from the operating fluid (water) is transferred to the heat or hot water circuit.

The separation of the two circuits prevents process carryover into the heat recovery system. This variant can also be used with other types of vacuum pumps with water-cooled motors. In the case of oil-air heat exchangers, the ambient air acts as a transfer medium for heat dissipation and recovery. This technology minimizes corrosion and maintenance costs.

The conditions in a centralized vacuum supply are particularly favorable for effective heat recovery. Because the vacuum pumps in this solution are installed in a separate room, the waste heat cannot access the cooled production areas to place additional strain on the air conditioning system. At the same time, thanks to the spatial concentration, a range of technologies allows the waste heat to be used comprehensively and efficiently.

The experts from Busch will help you to select the heat recovery technology best suited to your application.

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