ηmax Project

Refrigeration system engineering with leading-edge technology …
for a better global environment

Achieving○ηmax ＝∫ΔSminin Refrigeration

Ｒηmax Refrigeration SystemIn pursuit of precision emRS leads the future in refrigeration

What is the ηmax Project?
The Eta-max Project is dedicated to increasing the eﬃciency of refrigerator systems. The Eta-max team hasdeveloped an improved refrigerator system that increases eﬃciency and the coeﬃcient of performance (COP)
while maintaining the quality of frozen products. This is achieved by monitoring system and local environmentalconditions, determining (in real time) the ideal pressures and temperatures required for maximum
eﬃcient freezing and controlling these conditions. This allows the Eta-max refrigeration system (emRS) toreduce energy requirements by up to 50% and increase freezing capacity by up to 30% resulting in a more
economical and environmentally friendly system.
The project team at Nakayama Engineering has also cooperated with research institutes and Japanese
governmental agencies, facilitating the application of this technology to transportation and distribution systems
in order to save energy and reduce greenhouse gas emissions.
"Contributing to world-wide environment and resource protection by promoting our innovative refrigeration systemtechnology around the globe." This is the goal of Nakayama Engineering and its supporting partners.

Multidiscipline engineering System Development: Nakayama Engineering K.K.

Conventional freezing systems
Limited by technology

DISTRIBUTER

EVAPORATOR

unequal loading

Damage!!

Low tk and Small TD are the keys to perfect freezing
Todayʼ s refrigeration systems are plagued with a number of problems when operated at a condensationpressure of 0.9MPa to 1.1MPa or less, leading to a failure in freezing. This is because the distribution ofrefrigerant within the evaporator becomes so degraded that the refrigerant starts to backﬂow, damaging
the refrigeration unit. Cooling capacity is also drastically reduced, causing faulty freezing. When thetemperature diﬀerential (TD) between the refrigerant and the air is less than 10℃, the system cannot
produce suﬃcient freezing due to poor refrigerant control and reduced eﬃciency.
●

Limited condensation pressure: No energy savings from low outdoor temperatures●

Low condensation temperatures aggravate distribution within the evaporator, causing failure●

Reduced capacity due to frost on the evaporator, and energy loss due to frequent defrosting●

Increased sublimation within the product by exposure to high temperature diﬀerentials causes
quality deterioration because of drying

tk =condensation temperature

TD = temperature diﬀerential between the refrigerant evaporation and the ambient air

tk≧1.1MPa

TD≧10℃A standard for the future emRS pursues accuracy

For instance
R-717(NH3）
RT=-38℃
to=-40℃（70kPa）
tk=-10℃（300kPa）

DISTRIBUTER

TD=2℃
SH=1.5℃EVAPORATOR

equalize loading

Enable!!

The emRS diﬀerence: Refrigeration at a low tk and a small TD.
ηmax Refrigeration System operate at optimal eﬃciency even with a minimum condensationpressure(0.3 MPa) when the outdoor temperature goes down in winter. The same can be said when
TD falls to 2℃. The emRS unit always behaves in an ideal manner in accordance with load changes.
The result is as follows:

Synergy eﬀects from these three features:●Energy eﬃcient (less CO2) ……. Electricity consumption is reduced by 50%,while the freezing capacity is increased by 30%.

●

Suppressed frost formation on the heat exchanger …. Stabilization of freezer room
temperatures prevents freezer burn.

●Higher food quality through cryogenic freezing (-70℃)…….Virtually no change intaste thanks to ice crystals not rupturing cells.

tk≧to+0.3MPa

TD≧2℃

Energy Savings (reduction in CO2 emissions)
Outstanding eﬃciency in energy conversionp (MPa abs)

reduces environmental footprint
MR-404A p-h chart

AbsCONDENSER

normal tk=33℃

1.428

emRS tk=-3℃

0.555

EXP.V

normalemRS

0.425
0.397
0.185

normal to=-40℃

0.136

50％

normalemRS

Up to 30％

Reduction in electricity
consumption

normalemRS

Increase in freezing
capacity
180195343 350 373

395
COMPRESSOR

M

80
70
60
50
4030
20

enthalpy h (kJ/kg)
M

Dissipation power
Refrigeration capacity
Φo ,dissipation power (Kw)emRS to=-32℃100UNIT COOLER

p-h map of a two-stage compressor at a room temperature of ‒30℃

-104015
Condensation temperature tk (℃)

Electricity consumption and freezing
capacity by condensation temperature※Extrapolated from the performance table of a screw compressorof Mitsubishi Erectric with an evaporation temperature of to=-45℃
to=evaporative temperature (MSA-SP550A,55kW Two stage compressor)

Unprecedented energy savings in refrigeration, thanks to low condensation pressures.
It is common knowledge throughout the world that operating at a low condensation pressure will save energy. emRS utilizes
the dynamic programming of sophisticated mathematical algorithms in its design. The system actively reduces the condensationpressure to a level that is the lowest value possible for the condensation temperature, emulating the outdoor temperature.
This produces the following beneﬁts:●Reduced electricity consumption:
Smaller compression ratios in the refrigerator equipment mean reduced axial power requirements.
●Improved refrigeration capacity:
A decreased refrigerant liquid temperature and an increased speciﬁc enthalpy diﬀerential mean a larger freezing capacity.
●Longer life for refrigeration machinery:
Lower mechanical loads mean a longer overhaul cycle and longer mechanical life.
●Less greenhouse gas emissions:
Reductions of 41% in Kushiro, Hokkaido (sub-boreal climate); 26% in Chiba (temperate); and 16% in Okinawa (subtropical),all in Japan.
(Compared to our existing model where the pressure and temperature losses are set at our standard values.
The energy savings and emissions reduction will be larger if compared to conventional freezer systems.)

Integrated with advanced control systems
In pursuit of higher accuracy and precision
tk optimizer
Superheat controller

EXP.VMFＡ

電源
R S TMF

MF

MF

Inverter

ＣＢ

Ｄ

A:Unit cooler
B:Refrigeration unit
C:Condenser
D:Receiver
E:EXP.V
Temp sensorPressure sensor

tk optimizer ® feedback control tracks rapid load changes
If the condensation pressure is simply allowed to drop in tandem with the outdoor temperature, the evaporation temperature
increases when more load comes from the product or the room temperature increases at the end of a defrosting cycle. A higher
evaporation temperature represents increased freezing performance, which in turn increases the ﬁnal value of the evaporation
temperature, causing a larger pressure drop to be required. If the pressure is not large enough to cover the pressure drop, thenthe evaporation temperature drops, eventually producing an operation failure.
This is where tk optimizer ® comes in. It constantly monitors the operation of the evaporator and calculates the pressure drop
required for liquid refrigerant to reach an appropriate evaporation temperature. The Optimizer, in other words, performs afeedback control function by actively decreasing the condensation pressure to the limit of the pressure drop. The operation willthus be maintained at optimal levels, resulting in energy savings and high-quality frozen food.

● Constantly monitors the evaporator conditions● Optimizes the condensation pressure to the lowest possible level● Immediately follows rapid load changes● Allows for freezing capacity control

Frost suppression technology
Physical problems resolved by physical means

TD=2℃

TD=15℃-30℃-45℃-30℃ -32℃

＊
＊
＊
＊
＊
＊
＊

＊
＊
＊
＊
＊
＊
＊
＊
AIR FROST EVAPORATOR

AIR EVAPORATOR FROST
Direct expansion

Fight the biggest foe of freezers: frosting on evaporators
The biggest physical challenge in freezer systems is the buildup of frost on evaporators. Typically,
frost formation is assumed to be inevitable and has been solved through short-cycled defrosting
using hot gas or a heater. Frost occurs when moisture in the air in the freezer room condenses
and freezes on the surface of the evaporator. The larger the TD (temperature diﬀerential between
the surface of the evaporator and the ambient air), the more likely it is that frost will begenerated; this, in turn, increases TD. In conventionally designed systems, TD is usually set ataround 10 to 15℃ or higher, requiring frequent defrosting procedures. emRSʼ s high-accuracy,
low-pressure-diﬀerential refrigerant distribution technology has made it possible to maintain TD
to within 2 to 5℃. The result is drastically minimized frost formation.
●Frost suppression, thanks to a small TD within 2 to 5℃●Control of sublimation by a reduced diﬀerential between the evaporation
temperature and product (freezer burn is controlled)●Energy savings through a reduced number of defrostings●

Consistent freezer room temperature through a reduced number of defrostings

Higher Quality Food through Cryogenic
Processing Cell Structures Remain Intact
10Temperature[℃]0ηmax Refrigeration System Freezer（-70℃） Conventional Shock Freezer（-38℃）-10-20-30-40-50-60■Frozen muscle tissue (tuna: 60 mm thick)Source: Hokkaido Food Processing Research Center-70
0.0

0.5

1.0

1.5

2.0
Time[hour]

Maximum transit time in theice crystal generation zone

2.5

3.0

3.5

4.0

Time required to reach the coretemperature of ‒20℃

Conventional（-38℃） 55minutes

140minutesemRS（-70℃）

46minutes

6minutes■Changes in Core Temperature(Tuna at 60 mm in thickness)

Cryogenic Freezing: R-404a produces ‒70℃ for commercial applicationsWith a two-stage compression unit, a cryogenic temperature of ‒70℃ is now a reality
using a hydrocarbon refrigerant.
The quality of frozen food is dependent upon transit time in the temperature range where water in the cellstructure crystallizes (peak ice-forming temperature zone: -1 to ‒5℃). This is common knowledge in theindustry. The lower the internal tissue temperature, and with the right wind velocity, the shorter the timerequired for freezing. The shorter the time spent in the ice-forming temperature range, the less the damage
to the tissue in the freezing process. This is because the water will solidify into minute ice crystals without
rupturing the cell walls. Hence, a stable cryogenic temperature (below -60℃) is required for high-quality
freezing. Up until now, however, special freezing methods such as nitrogen freezing or dual freezing havebeen required to achieve this. ηmax Refrigeration System has succeeded at consistently operating thefreezing process at a cryogenic temperature using the conventional freezing principle by developing alow-temperature diﬀerential operation.

● Improved quality of frozen food as a result of small ice crystals within the cells.
● Achieve cryogenic temperatures by using a conventional freezing system (two-stage compression)● Signiﬁcant enhancement of freezing capacity achieved by powering up smaller units equal to orbetter than units one or two sizes larger.

TD=15℃-72℃
EVAPORATOR

-57℃
AIR

TD=2℃

-72℃
EVAPORATOR

-70℃
AIR

Products

For any refrigeration and cooling systemtk optimizer

NewemRS Rack Freezer

emRS Batch Freezer
emRS also oﬀers a wide selection of freezers
for any application, ranging from a compact
50 kg/h to as large as 40metric tons/Day.
Thanks to newly developed frost control
technology, these freezers deliver exceptionalreliability and easy temperature control. With
their high-speed freezing capability, you canmake your product freezing schedule highly
eﬃcient and even save storage space!
Temperature range:-20℃ to -70℃

With Cascade system:-70℃ to -100℃

The batch type ultra-low temperature freezer is
CE certiﬁed.
You will be able to purchase it in the EU area as
it complies with European standards.
The simple design makes it highly reliable andalso greatly reduces the risk of system failure.
Temperature range:-20℃ to -70℃

山路を登りながら

emRS CO2 Cascade System

The CO2 direct expansion freezing system has
been successfully developed for commercial
usage. With all the excellent characteristics of
the CO2 refrigerant, we are able to maximize
its full capability with our system.
With a compact and highly reliable compressor,
it is now possible to implement our CO2 system
to small scale cold storages which require
smaller cooling capacity as well.

emRS Reefer Container

By using η-max technology, a normal reefercontainer can be transformed to achieve theultra-low temperature range of 5°
C to -60°
C
while maintaining a high eﬃciency operating
condition.
Temperature range:

More Information:www.refrigeration.jp-20℃ to -60℃

We are just a call away…
NewemRS Cold storage warehouse

emRS Continuous rapid freezer■Cold storage warehouse■Spiral/tunnel type freezer

Capable of operating with minimum
temperature diﬀerentials and with temperature
ranges from chilling to ultra-deep freezing, thisstocker features rapid and infrequent
defrosting with a lower operating cost andextended retention of product quality.

Temperature increases due to frost have been
the number one problem confronting
continuous rapid freezers. Our system, completewith steel conveyor belts designed for massprocessing, successfully prevents temperature
increases and consistently maintains a target
temperature, thanks to the synergy eﬀect
between the frost control technology and theoutdoor air control technology. It is designed forhigher productivity and increased quality as well
as for better space utilization.

Operating temperatures:With cascade system:

5℃ to–70℃-70℃ to–100℃

Temperature range:+10℃ to ‒60 ℃

Other Products

emRS Unit Cooler■emRS Refrigerated Ship■emRS Testing Device■ emRS Condensing Unit

The unit cooler is the most essential
component of any refrigeration system. Our
unit cooler has been built to our proprietary
design, including cutting-edge refrigerant
distribution technology that evenly supplies
low refrigerant ﬂows to multiple circuits. It
also features pressure loss reduction
technology with optimal circuit lengths.

Consulting･R&D■Technology consulting■ Cold Chain※The unit is custom-built to meet the needs of any
specific application, ranging from refrigeration to■Retrofit

ultra-deep freezing.

■ Frozen Foods Development

More Information:www.refrigeration.jp

ηmax Refrigeration System

Multidiscipline engineering System Development:

Nakayama Engineering K.K.
7-5 1-chome, Tozuka, Kawaguchi City, Saitama Prefecture JAPAN
Telephone: +81-48-295-2010

Facsimile:+81-48-295-2545

Subsidiary:

TdS Refrigeration Systems GmbH
Landsberger Str.302

80687, München

AG München,HRB 236304 GERMANY
Telephone:+49-159-01210025
info@tdsrefrigeration.dewww.refrigeration.jp

For more information, please contact us or the following dealers:emRS dealer: