Industrial heat pump design

The key technical parameter when designing an industrial heat pump is the temperature difference – i.e. the difference between the source and sink temperatures. The smaller this difference, the more efficiently the heat pump works. The coefficient of performance (COP) indicates how much heat is provided per kilowatt hour of electricity used – and decreases as the temperature difference increases.

For a realistic interpretation, the following questions must be answered:

• How stable are the source temperatures over the course of the year?
• What temperature level is actually required on the sink side?
• Is a single-stage process sufficient or is a cascade required?

An understanding of thermodynamic behaviour in the Th diagram helps to correctly define evaporator and condenser conditions and select suitable refrigerants.

Industrial plants often have waste heat sources that are ideal for use with industrial heat pumps – provided that the temperature, volume flow and availability are suitable. Frequently used sources are:

• Recooling systems (e.g. for refrigeration systems or compressors)
• Cooling water from reactors, presses or vacuum pumps
• Exhaust air flows from drying or cleaning processes
• Wastewater or process wastewater from CIP systems

There are many possible applications on the sink side:

• Hot water supply for cleaning, space heating or production
• Preheating of fresh water or air flows
• Steam generation with high-temperature heat pumps
• Feed-in to internal or external heating networks

The crucial factor is that the source and sink must match each other in terms of temperature level, volume flow and time progression. Careful analysis of these parameters forms the basis for an economically and technically sound design.

The integration of an industrial heat pump should never be considered in isolation. It is part of a larger system – with existing heat sources, recovery facilities and possibly conventional heating. The following points are therefore key to successful planning:

• Energy system analysis: Is heat recovery already in place? Where are the source and sink potentials in the process?
• Operation and control: How does the heat pump behave under partial load? Are there any cycles?
• Technical constraints: space requirements, sound insulation, connection to the process control system
• Cost-effectiveness: What is the balance between investment, electricity costs and subsidies (e.g. BAFA subsidy, federal subsidy for efficient heating networks)?

Only when the heat pump is properly integrated into the overall system – in terms of energy and control technology – can it realise its full savings potential.