Vapor Quality
How Vapor Quality Control Can Cut Part-Load Energy Use by 40%
Written by: Jae O. Haroldsen
Originally published by: NaturalRefrigerants.com
HB Products’ control system adjusts refrigerant feed based on liquid leaving evaporators in ammonia, CO2 and hydrocarbon systems.
Vapor sensor control could cut energy consumption by roughly 40% for part-load refrigeration operation compared to self-regulating systems designed for full-load efficiency, according to Henrik Kudsk, Product Manager at HB Products.
The Danish component manufacturer produces sensors for industrial and commercial refrigeration and heat pump applications, primarily serving large-scale systems with capacities of 500kW (142.2TR) or more. Its refrigerant-agnostic products provide evaporator, level and oil-management controls for systems using natural refrigerants, including ammonia (R717), CO2 (R744) and hydrocarbons.
“We see ammonia installations in Europe, South America and the U.S. where contractors just want to use the same liquid pump system that they did 20 years ago,” Kudsk said. “With vapor control, you can make a smaller system with less ammonia and still have the same efficiency and capacity as the uncontrolled larger system.”
In 2025 a German cold storage facility incorporated HB Products’ vapor sensor control into a direct-expansion (DX) ammonia refrigeration system. Compared with a similar site nearby using pumped liquid overfeed, the system reduced energy consumption by 23%, according to HB Products.
Kudsk recently spoke to NaturalRefrigerants.com about incorporating HB Products’ vapor sensor control in new and existing systems, as well as market trends for applications across the globe.
The interview has been edited for length and clarity.
What efficiency issues do you see, and how can your technology improve year-round operation?
Henrik Kudsk: The technology, particularly for large-scale ammonia systems, has been around for so long that contractors are comfortable reproducing conventional systems, designed to be efficient at full load, with a large vessel and pump supplying liquid ammonia to evaporators. However, cold stores generally operate at full load only during summer months, when a lot of goods enter the facility. In industry processing applications, freezing loads can also vary substantially, with high loads early in the freezing process followed by lower loads as more heat is removed from the product and the load shifts towards temperature maintenance.
In part-load operation, less heat is available for refrigerant evaporation. If you don’t significantly reduce the liquid supply, more liquid will leave the evaporator, needing transportation back to the pump separator. Since the compressor is the engine for this process, it has to work harder, consuming more power than necessary.
Our system consists of a sensor that measures the amount of liquid leaving the evaporator and a PLC controller that uses that measurement to regulate liquid feed into the evaporator through a control valve. We maintain a constant amount of liquid exiting the evaporator. This is what we call vapor quality control, and it works for all refrigerants and for any circulation rate. With vapor control, the evaporator can provide greater effective cooling capacity at part load because the liquid feed is better matched to the available heat load, improving heat transfer.
Does your solution apply to both new builds and retrofits?
HK: Of course, it is easier to implement the technology if you do it from scratch. However, one of the biggest advantages for retrofits is that if you have a refrigeration system that is too small for an expansion of your manufacturing facility, you can actually increase the system’s capacity and add evaporators using our vapor sensor controls. With our sensors, you can use a smaller separator because you don’t need to maintain as much liquid refrigerant sitting in the suction lines.
Retrofits of large systems are more complicated because the worst evaporator defines the required suction pressure. This means that you can’t optimize one evaporator and achieve large savings unless it is the bottleneck. You must analyze and map the entire system to get optimal operation.
It takes effort and some money to develop the vapor sensor control algorithm for individual applications, but, for large systems, the cost is peanuts compared to the energy savings. With systems operating for 20–30 years, a 40% energy reduction can represent an enormous amount of money.
What industrial refrigeration market trends does HB Products see around the globe? What projects are you participating in?
HK: Currently the biggest market for our vapor sensors is Australia. They are building DX ammonia systems that evaporate all of the liquid refrigerant. Instead of using a final low-pressure liquid separator, they use our sensor to make sure there is no – or only a tiny bit of – liquid leaving the evaporator. For DX systems, the sensor supports roughly 20% energy savings in full load and 50% in part load – compared to superheat control.
In addition to cold storage and industrial applications in Europe and the U.S., we see many ammonia systems in Latin American countries such as Colombia, Chile and Mexico, especially for food processing. We are also supporting projects with propane [R290] and butane [R600], as business with hydrocarbons is growing rapidly. Ultimately, we want to help contractors and end users, wherever they are, understand that installing large refrigeration systems without vapor control may be slightly cheaper initially, but energy consumption can be much higher.
The technology is also being applied beyond refrigeration. Our vapor-quality sensor has been installed in a huge heat pump in Switzerland. For efficiency, the engineers want to know how much liquid they are dealing with. It is hard to measure roughly 3mm (0.1in) of still-boiling ammonia at the bottom of a large pipe while the gas is moving at 25m/s (82ft/s). With our sensor, we can get a number and maintain the level both in full and part load.
This article was originally published by NaturalRefrigerants.com and is republished here with kind permission. Read the original article here.
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