a Floating Head Pressure Technology, HY-SAVE

Liquid Pressure Amplification (LPA)
A Floating Head Pressures Technology without a loss in TEV or
EEV Capacity: Becker/O’Brien, 2008, UK

Definitions
EEV = Electronic Expansion Valve.
TEV = Thermostatic Expansion Valve.
As head pressure is dropped:
The compressor would tend to unload because:

As head pressure is dropped

The compressor would tend to unload because:

• Liquid temperature hence liquid enthalpy reduces giving increased specific refrigeration effect allowing a reduction in mass flow.
• Compressors swept volume would increase due to increased volumetric efficiency brought about by reduced compression ratio (Clearance Pocket). The compressor would consume considerably less power because:
• Reduced compression ratios means for reduced power consumption per unit weight refrigerant circulated.
• The compressor unloads because the weight of refrigerant circulated has reduced due to increased specific refrigeration effect.
• The compressor unloads due to increased compressor volumetric efficiency. The effective compressor power savings (kW/kW) when lowering head pressures from 43°C SCT to 20°C SCT is often in the region of 60%.

Changes affected by thermophysical dynamics

Whenever there is a reduction in liquid enthalpy or a reduction in system refrigerant flow by compressor capacity staging there tends to be an increase in evaporator operating charge. This is to say there is refrigerant charge redistribution from condenser to evaporator. This low liquid enthalpy induced refrigerant redistribution results in both EEV and TEV starvation at a time when their capacities are already cut somewhat by reduced pressure drops.

Refrigerant property changes in the condenser

With the drop in condenser operating pressure there is an accompanying vapor density drop.
Saturated R22 vapor in the condenser at 43C has a density of 71.62 kg/m3 but then at 20C has a lower density of 38.34 kg/m3.

This density change tends to achieve an increase in a liquid line liquid mass. Though any such increase is quickly offset by other factors discussed below. Also, with the subsequent reduced liquid temperatures there is an increase in liquid line liquid density acting to free up liquid line volume, this effect somewhat accommodates the above mentioned increased mass there. R22 liquid density at 40C is 1131.58 kg/m3 while at 20C is increased to 1213.37 kg/m3

Refrigerant property changes in the evaporator

Any time there is a reduction in evaporator flash gas there will be an increase in evaporator operating refrigerant charge. Variables affecting a reduction in evaporator flash gas are a reduction in refrigerant mass flow by compressor capacity staging and/or a reduction in liquid enthalpy. An analogy here would be boiling water, the greater the rate of heat input the greater the degree of boiling. Greater boiling is merely a greater rate of evaporation and tends to increase the waters specific volume effectively raising the waters wet level. The waters wet level then of course drops with reduced boiling. If a TEV were used to maintain a wet level then with reduced boiling more refrigerant mass would be required to maintain that wet level. By floating the head pressure i.e. allowing the head pressure to drop with falling ambient temperatures; we affect a reduction in both compressor capacity staging and liquid enthalpy. The resulting increased evaporator operating charge, in most cases, is greater than any increase in liquid line mass from reduced condenser vapor density. Overall system refrigerant mass redistribution by reduced evaporator refrigerant quality most often affects a reduction in liquid line mass to the point where expansion devices are liquid starved. Any expansion valve, EEV or TEV, has its capacity considerably reduced when starved of refrigerant, when not being fed by a solid liquid seal.

Comparing EEV and TEV when floating head pressure

With the speculated saturated condensing pressure drop from 43C to 20C there is a reduction in available TEV pressure drop, an increase in available liquid density and a reduction in liquid enthalpy. With these three changed aspects considered it could be estimated that:

• EEV capacity loss may be in the region of 20%
• TEV capacity loss may be in the region of 28%.
  With both TEV and EEV, capacity is subject to available liquid quality. It has to be guaranteed that there is a solid liquid head available at the EEV or TEV inlet. The occurrence of liquid line vapor is especially increased with liquid line component pressure drop or line lift while also ambient or solar thermal gains will contribute. While the EEV may have the ability to open further with increased superheats, this also has the adverse effect of further increasing liquid line component pressure drop caused by accelerating the liquid/vapor mix. This increased pressure drop has to result in increased liquid line vapor. Some EEV manufacturers suggest the inclusion of a control characteristic to cycle condenser fans in the event of low load and/or low ambient valve liquid starvation occurring as a result of liquid line vapor. These manufacturers hereby recognize the system refrigerant redistribution, which occurs with floating heads.

Subcooling to eliminate liquid line vapor

Liquid saturated ∆T/∆P ratios increase considerably at the lower 20C conditions such that for any given liquid line static or component pressure drop an increase in subcool by some 56% is required. Even with the reduced mass flows resulting from increased specific refrigeration effect this factor must still be considered. This increased ∆T/∆P effect on liquid line lift is not changed by reduced mass flow following increased refrigeration effect, in fact it is worsened by liquid density increase. Further, with increased compressor COP comes reduced condenser TD and therefore a reduced available subcool margin.
Increasing system refrigerant charge to overcome the above then generally demands that there be an increase in head pressure back somewhat above the ideal. Increased refrigerant charge may also result in unwanted condenser flooding during high loads at designed ambients effectively raising head pressures above design. The reduced liquid to suction line temperature difference reduces suction/liquid heat interchange capacity. This is especially so if it is intended that saturated refrigerant pressures are dropped even further below the already speculated 20C, which is most often the case. Optional heat interchanges required for these low liquid to suction temperature differences may be so large as to make their use wholly impractical.

Liquid Pressure Amplification

Primarily LPA is about achieving floating head pressures. On DX systems a liquid line pump is added to the liquid line in order to maintain expansion device design operating pressure difference while head pressures is permitted to float with colder ambients. The pump also provides added subcool, by pressure amplification, needed to match the increased saturated refrigerant ∆T/∆P ratio.
Of course, with LPA a small additional charge quantity may be necessary to ensure at least 1K sub-cooling at pump inlet. However, this charge addition is far less than the extra charge needed to achieve required subcool for the same liquid line pressure losses without the use of a pump. The inclusion of a liquid line pump can provide for re-condensing of the liquid line vapor portions mentioned earlier in this article. In addition, it obviously raises liquid pressure, which in most cases acts to re-establish design EEV and TEV pressure drop. The advantage here then is that in many instances the cheaper and more proved TEV could be used in preference to the EEV. A carefully sized capillary can be installed parallel to the TEV to supplement TEV orifice size when design valve pressure drops are still not being achieved. Even when floating head pressures there are still often head pressure constraints requiring head pressure control only at some lower limit. Considering the colder liquids increased saturated ∆T/∆P ratio, head pressure controls cycling in and out can cause a “frothing” of the liquid line again reducing EEV and TEV capacity. The liquid pump will most often clear this liquid line frothing.

Becker/O’Brien, Westfield Estate, Midsomer Norton, UK 2008

about liquid refrigerant pumping (LRP) is a simple, reliable way to improve refrigeration efficiencies. this technology modifies a conventional direct expansion (DX) refrigeration
system in such a way that average compressor load is reduced and cooling capacity is increased.

For an evaporator to operate efficiently, it must operate with as high percent of liquid-to-vapour ratio as possible. To accomplish this, the Expansion Device must be able to regulate the flow of liquid refrigerant into the Evaporator at the same rate at which it evaporates. As seen in most systems, the overfeeding and underfeeding of the Expansion Device drastically affects the efficiency of the Evaporator. With the LPA system installed and running, the flow rate is consistently higher with a more evenly modulating Expansion Device. The increase in refrigerant flow and improved control of the expansion device provides

LPA and the expansion devise

The application of Liquid Pressure Amplification (LPA) to a refrigeration or air conditioning system provides the means by which a considerable reduction in Compressor Discharge Pressure can be permitted. Liquid Pressure Amplification (LPA) is achieved by an semi hermetically sealed, magnetically driven liquid refrigerant pump which is installed in the Liquid Line from the condenser (or Receiver) and thus sits between the Condensing and Evaporative phases. By overcoming the Liquid Line Pressure Drop, Flash Vapour can be completely eliminated. 

LPA Pressure Enthalpy Chart

HY-SAVE’s technology, particularly the use of LPA (Liquid Pressure Amplification) pumps, is designed to enhance the efficiency of refrigeration systems while also addressing the common issue of scale build-up in water-cooled systems. By reducing the compressor’s discharge temperature by 50K (180°F), the LPA pumps help to prevent scale from forming on the condenser tubes within cooling towers and water-cooled condensers as the discharge temperatures are below the temperature that scale forms.

Discharge de-superheating.

keywords, liquid injection, superheat suppression, evaporation tower, water cooled condenser, compressor discharge temperature, reduction, heat extraction, outdoors

The implementation of LPA (Liquid Pressure Amplification) technology by HY-SAVE and Dixell (Asia) in the supermarket sector across Thailand has led to significant energy savings. Despite the high outdoor ambient temperatures, which can reach up to 40 degrees Celsius (105F) during the day and 30 degrees at night, Dixell (Asia) has reported an impressive 15% to 25% improvement in refrigeration efficiency.

What others are saying about HY-SAVE Technology

Carrier (Thailand) has been recognized for their role in the LPA installation, with Dixell (Asia) monitoring the program throughout its implementation across Thailand. This successful roll out not only demonstrates the potential for energy savings in the supermarket refrigeration sector but also highlights the effectiveness of LPA technology in tropical climates where cooling demands are high.

Liquid Pressure Amplification – Refrigeration energy savings.

DX free cooling, or economized cooling, is a smart and energy-efficient method that leverages lower outdoor temperatures to minimize the reliance on mechanical refrigeration. By using an LPA pump to circulate the refrigerant when conditions are favorable, the system can effectively transfer heat outside, bypassing the energy-intensive vapor compression cycle.

This process not only saves energy but also extends the life of the compressors by reducing their workload during cooler periods. It’s an example of how innovative engineering solutions can lead to more sustainable and cost-effective operations in HVAC systems.

DX free cooling systems are particularly suitable for applications where heat extraction is critical, such as in data centers, server rooms, remote electrical switch-gear, underground rail systems, subways, or rail networks. They can handle production cooling capacities ranging from 15 to 150 tons per circuit, making them versatile for various industrial and commercial settings.

Upgrading a refrigeration system can be complex and requires a thorough understanding of the system’s design, operation, and the specific technologies involved, such as Liquid Pressure Amplification (LPA). A qualified engineer will have the expertise to ensure that the upgrade is done correctly, safely, and in a way that maximizes the system’s efficiency and performance. It’s always best to rely on professionals when making significant changes to specialized equipment.

The combination of HY-SAVE technologies, including Liquid Pressure Amplification (LPA), and compressor discharge heat reclaim & disposal can lead to significant improvements in refrigeration efficiency, especially in hot climates. These technologies work together to enhance the performance of refrigeration systems by ensuring optimal refrigerant flow and utilizing waste heat effectively.

The compressor discharge heat reclaim upgrade captures waste heat from the compressor discharge which can be a larger proportion of the THR by the condenser improving the system’s efficiency substantially.

In hot geographical locations, where cooling demands are higher, these technologies can help reduce the energy consumption of refrigeration systems, which is a major contributor to overall electricity usage. By improving the efficiency of these systems, supermarkets and other food retailers can significantly lower their operational costs and carbon footprint, contributing to a more sustainable future.

As a result, the system’s refrigeration efficiency can improve by 15 to 25%, which is a substantial increase, particularly in systems that have been operating inefficiently or have limited condensing duty. This upgrade not only reduces energy consumption but also extends the lifespan of the equipment by reducing wear and tear on the compressor and other components.

In summary, the LPA® pump is a valuable addition to refrigeration systems, especially in scenarios where the design has led to inefficiencies that can be rectified by installing a LPA pump. It’s an effective solution for achieving energy efficiency and sustainability in the refrigeration industry.

HY-SAVE’s commitment to research and development in the field of energy-efficient refrigeration design and operation has had a significant impact on reducing carbon emissions. Their advancements in system performance are not only enhancing efficiency but also contributing to substantial environmental benefits. The collective savings of over 300 million tons of CO2 annually is a remarkable achievement.

Looking ahead, the projection of reducing carbon emissions to around 485 million tons annually by 2030 is an ambitious and commendable goal. This reflects the potential of HY-SAVE’s technologies to make a considerable difference in the fight against climate change by reducing the carbon footprint of refrigeration systems worldwide.

In March 2023, HY-SAVE introduced the higher duty model 975, a significant advancement in their pump performance lineup. This model is designed to enhance flow rates, exceeding 110 GPM (Gallons Per Minute), which is indicative of its capability for reliable and high-performance refrigeration heat transfer applications. The model 975 is set to be available in Fall 2024, promising to be a valuable addition to the industry, especially for those seeking to improve the efficiency and effectiveness of their refrigeration systems.

In October 2023, advancements in CO2 trans-critical circuits have led to a reconfiguration of system circuits to operate without liquid receivers. This development allows for a smaller overall package footprint, enabling higher tonnage per square foot for various applications, whether it be in the industry, commercial, or residential sectors. The elimination of liquid receivers simplifies the system design and can potentially reduce installation and maintenance costs while improving system efficiency. This is particularly beneficial in space-constrained environments where maximizing the use of available area is crucial. The ability to achieve higher cooling capacities in a compact space aligns with the ongoing trend towards more efficient and sustainable refrigeration solutions.

Stepping back 1984

Celebrating 40 years in the refrigeration industry…

1984-Company founded, Portland, Oregon, USA by Inventor Bob HYDE

• First development and production of liquid line refrigerant pumps (for Freon) to “ensure 100% liquid” at the liquid metering device regardless of liquid line vertical height or pressure drop and associated liquid line flash gas.
• HY-SAVE® technology established as a method of improving refrigeration efficiency.

 1986-First patent “Maximizing Refrigeration Capacity and Performance”

• LPA pump (Liquid Pressure Amplification) introduced and established as slogan, trademark and brand
• Sales and distribution for LPA pumps begin

1987-US distributor agreements

• Distributors appointed USA & Canada
• New style brochure “Tomorrows Refrigeration Technology Today” introduced

1989-Partner with US Gov. FEMP to support and document product efficiency and case studies

• Introduced energy saving analysis and methods of determining efficiency
• Improved performance and re-design of model 835 LPA pump
• Improved model 850 for higher working pressures
• Launched Stainless Steel Model 875 (Made  in America)
• UL pressure strength and fatigue testing of models 809,815,820,833,860,875 recognized

1990-New efficient TEFC motors for tougher environments tested

• Introduced new testing platform, improved quality and R&D

1992-HY-SAVE Inc. appoints representation in Florida, Key West and the Caribbean

• Testing of liquid Injection into compressor cylinder heads for cooling began.
• De-superheating of compressor cylinders using LPA pumped refrigerant started

1994 HY-DRY de-humidification process, established and patented

• Established automated selection and sizing program to project efficiency
• Filed numerous patents to protect LPA pump performance and operation
• Set up and established refrigerant two phase flow research with LPA as a means of providing heat transfer between mediums know today as DX free cooling
• Expanded the network of regional distributors
• Increased Horse Power of model 850 0.5ph to model 860 0.6hp

1996 Plus 2 system for higher efficiency developed and patented

• Expanded testing platform to include multi coupled pressure points
• Improved facility to provide distributor and customer support

1998 HY-SAVE IP, patents, designs and technology acquired by DTE Energy Technologies, Michigan, USA

• Introduced first Pump-Pro 1 electronic pump controller that monitors and controls the induced pressure developed by the LPA pump to control and protect against abnormalities in a refrigeration system.
• Developed new methods of heat transfer and system efficiency with two phase cooling mediums and methods today known as DX Free Cooling

2000 HY-SAVE organization of regional and international distributors and OEM’s established

• Energy efficient refrigeration research and development taken global
• Established PP2 Version 2, as a method to protect LPA® pumps from running dry based on induced liquid differential pressure and quality of liquid entering the pump

2003 HY-SAVE acquires IP, patents, designs, trademarks, existing agreements and technology from DTE Energy Technologies, Michigan, USA

• Terminated US distributor lack of performance re organisation of existing channels
• Continued research and development of LPA technologies including two phase non vapor compression cooling systems
• Reorganized US manufacturing, introduced new stringent process and quality control for production requirements
• EU PED Certification for Models 833, 860 and 875 complience introduced

2005 Assembly plant transferred to Europe from Portland, Oregon, USA

• Improved distributor network
• Enhanced the range of HFC LPA pumps for higher operating pressures

2006 HY-SAVE USA opens in Tampa, Florida

• Launched cost effective remote energy monitoring device with built in Ethernet and GPRS
• Continued development of new methods to remove moisture in cold rooms in combination with HY-DRY

2007 UK Pressure testing facilities enhanced to accommodate natural refrigerant pressures and process control

2008 HFC range of LPA pumps redesigned for higher operating pressures

• Introduced more stringent quality control and specifications
• Launched 3^rd generation pump protection and control
• Enhanced range of LPA pumps compatible with Co2 pressures

2009 HY-SAVE offices open in Dandong, China

• Reviewed range of LPA pumps for added strength
• Introduced mass manufacturing and control process of LPA pumps

2010 Pump Protection module 3 to include free cooling operation and protection launched

2011 Automated energy monitoring to precisely measure energy consumption launched

• Model 925 LPA pump for HFC and Co2 applications, maximum working pressures at 50 bar (725 psi) introduced

2012 Official launch of model 925 for cascade Co2 applications

• Production of model 809 for manufacturing to suite a wide range of domestic / light commercial Co2 refrigeration applications.
• Engineered solutions to overcome -40F working temperatures specific to model 925
• Consultation with Engineering propose new model 975 to accommodate single circuit 400 tons refrigeration energy savings with LPA®
• UL Fatigue and Pressure testing of model 925 certification awarded

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2013 Design and development of Phase 1 solar refrigeration with ejector LPA® pumps

• Development of LPA® Liquid Refrigerant Pump boost liquid pressure 145 feet with ejector evaporating temperatures of (15F) annually.
• Continued development and completion of super critical Co2 liquid pump design working pressure, 124 bar (1,800 psi) flow rate region o1 to 9GPM

2014 Official launch of LPA® Model 809-NH3

• Testing of Liquid Injection Screw compressors port for compressor cooling in high ambient countries.
• Design and development Ammonia fluid LPA® pump for natural refrigerant applications. Design pressure rated at 540 psi
• Design and development world’s first in-line and auxiliary (TES) Thermal Energy Storage solutions for air conditioning and refrigeration systems
• Development of new type Propane LPA® pump for greener refrigeration application
• Development of Sub-Zero -40F LPA Model 860 for Arctic environments

2015 “Refrigeration on Demand” ™ The Thermal Storage Option introduced

• Design and development higher pressure model 860-SS-080 rated at 80 bar for Co2 DXFC applications
• Continued development model 875-SS-080 high pressure hold capacity LPA® pump Co2 applications

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2016 “Compressor cooling” introduced

• Set up, development thermal store, latent source thermal storage DX refrigeration storage & solutions, energy reduction in overall power consumption
• Introduced DX free cooling for split air conditioning units, including wall and ceiling mounted indoor units established for intense heat extract applications

2017  Development range of Dual Stage (DS) Co2 Liquid Pressure Amplifiers solar AC

• Model 833 rated 80 bar (1,087 psi) design operating pressure, self unloading, power 0.5HP
• Model 820 rated 80 bar (1,087 psi) design operating pressure, self unloading, power 0.3HP
• Range of DX Free Cooling split air conditioning units for with low power consumption and high efficiency
• Established DX plate type latent heat thermal storage patent & sub applications

2018 Patents awarded, Plate Thermal Storage for Air Conditioning used in conjunction with DX Free cooling for low energy thermal cooling for future generations

• Expansion of HY-SAVE’s production area includes R&D, testing, proto-typing, environmental testing sector & quality management
• Helium leak detection implemented quality control set up and introduced

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2019 Dual Stage model 820-DS introduced

• The 820-DS performance, measurement, certification ended

2020

• Implementation of post Brexit UK equivalent of the PED HPiVS CE2810 (Directive 2014/68/EU)  and  CE1521 for the UKCA, United Kingdom.

2021 Refrigerant based version and series LPA pumps upgraded to include Co2 & Nh3 fluids 80 bar design began.

• Variant K65 connections approved higher operating conditions provided PS PED/UKCA 80 bar / 200 bar

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• 2023 coming up