Why flow control is key to heat pump efficiency and performance
Keen to unlock the full potential of your heat pump? Well, flow control is absolutely key when it comes to heat pump efficiency and performance.
Here, we’ll explore how balancing flow rates can make or break your heating system – and why it matters more for heat pumps than boilers.
Flow control in heat pumps
Heat pumps generate heat through a refrigeration cycle, transferring it to water via a heat exchanger, which then distributes the heat throughout the building system.
For this process to work efficiently, the flow of refrigerant and water on either side of the heat exchanger must be balanced.
If not, the heat pump will either malfunction or operate inefficiently.
Why does flow control matter so much for heat pumps?
Heat pumps are more sensitive to water flow rate than gas boilers due to the fundamental differences in how they generate and transfer heat.
Gas boilers are less sensitive to water flow variations and are largely unaffected by water flow rate within a typical operational range.
This is because they don’t rely on optimising heat transfer through a refrigerant cycle – and they can stop and start heat production faster.
On the other hand, in heat pumps, the temperature difference between the refrigerant and the water are a lot smaller.
Refrigerants have specific thermodynamic properties that limit output temperature, input temperature, or temperature differential, depending on the type.
These constraints dictate the temperature and flow conditions on both sides of the heat exchanger.
Calculating flow rate
To ensure optimal performance, the system designer must match the heating system temperatures with those of the heat pump.
Once these temperatures are defined, the water system’s flow rate is calculated based on the heat pump’s maximum output at design ambient conditions.
As building heating demand fluctuates, the water flow rate must adjust to maintain the desired flow temperature and temperature differential (TD).
In systems with multiple heat pumps, the flow must be balanced between them.
The designer should select a pump capable of delivering the required flow rate, accounting for the total pressure drop across the entire water circuit (pipes, fittings, valves, heat pumps) and also define the flow control method including how flow will be measured.
Achieving flow control
Flow control can be achieved through pipe design (e.g. reverse return) and balancing/control valves, with pressure-independent control valves simplifying the process.
Flow measurement tools include manometers on commissioning sets, orifice plates, heat meters, or ultrasonic flow meters.
Before commissioning the heat pump, the design flow rates must be measured and proven at each heat pump.
This step is essential with heat pumps – whereas, with gas boilers, the greater tolerance of flow rate variance means it can be skipped with only minor efficiency impacts.
This flow control issue is one of the most fundamental, yet seemingly minor, changes the heating sector has to navigate in order to make heat pumps successful.
Let us worry about flow control for you
As you can see, there’s a lot to consider when it comes to flow rate and control in heat pumps.
But that’s not something you should have to worry about.
At Clade, we’ve been manufacturing heat pumps and refrigeration equipment for 35 years – so, we know what we’re talking about when it comes to flow control.
Our experienced designers, installers and commissioning engineers can create a heat pump system bespoke to your needs and ensure the flow rates are calculated and balanced just so.
Simply get in touch to start the process.