Figure 1: Heat pump and refrigeration cycle
Heat pump mechanism

Heat pump performance
Thermal energy
300-600

40℃
Thermal energy
300-600
Heat release③ Heat released to air
60℃

50℃

Coefficient of
performance (COP)= Efficiency= 3-6

Temperaturedecline
2℃-10℃
Evaporation

Motor

Condenser
gas

Condensation

Electricity
100

LiquidPower
Compressor

Heat exchanger
0℃
Fan
Heat
absorption

Gas

Pressure
Expansion andtemperature decline

22℃

60℃
Temperature
riseElectricity
100

Expansion
valve

Refrigerantgas

LiquidRefrigerant
gas

50℃

Expansion Refrigerantliquidvalve

Condensation

Thermal energy
200-500

7℃

In case of heating: Temperature of each part shows an example andvaries depending on operating conditions (volume ofrefrigerant circulated, air flow).

Unit heat quantity

Evaporation
Evaporator
LiquidPressurization andtemperature rise
② Compressive power

Gas

-10℃
① Heating byoutside air

0℃

Mollier chart
Thermal energy
200-500

A

B
C

For efficiency
improvementof heat pumps① Bring condensation temperature close to evaporation
temperature.
② Expand the range of supercooling and superheat
degree as much as possible.
③ Improve compressor efficiency.
④ Improve motor and inverter efficiency.
⑤ Control output changes and achieve sophisticatedcontrol.
⑥ Reduce auxiliary power and power loss.

COPh = C/B for heating ← Refrigeration cycle efficiency
COPc = A/B for cooling
Heat pump efficiency = Refrigeration cycle efficiency x compressor
efficiency (insulation efficiency, volume
efficiency) x motor efficiency* Consideration also given to auxiliary power

Figure 2: Merits of unused heat sources
Necessary temperature forheating: 45℃

Positioning of air,groundwater and aquifer
thermal energy as heatsources

Seasonal
thermal storage

Seasonal
thermal storage

Warm in winterCool in summer

It becomes cooler insummer and warmer
in winter in seasonal
thermal storage.
← Groundwatertemperature(about 19℃) in
Osaka city center

Temperature

Seasonal
thermal storage
Necessary temperature forcooling: 7℃
Jan. Feb. Mar. Apr. May Jun.
Maximum
temperature (℃)

Sewage heat is warm in
winter and is not so muchdifferent from airtemperature in summer.

Jul. Aug. Sep. Oct. Nov. Dec.

Averagetemperature (℃)

Heat pump efficiency
declines as thedifference between
heat source
temperature andsupply temperature
becomes large,
because heat pumps
require more power.

Minimum
temperature (℃)

Monthly average temperature and sewage
temperature in Osaka (example)♪

Places to obtain heat”””

Outdoor temperature
5℃

””

”

Outdoor temperaturein cold region-10℃

More power is required in cold regions.
In addition, water cooled heat pumps areunusable due to water freezing.

♪

”

”

”

Groundwater temperature
19℃

Places to dump heat

45℃”

Aquifer thermal energy
25℃

Heating

Cooling
7℃
The same idea is applicable in case of using sewage wateror river water.

Outdoor temperature
35℃
Groundwatertemperature
19℃
Aquifer thermalenergy8℃

Figure 3: Types of renewable energy and positioning of unused energy- Advantages & disadvantages, stability and controllability of various renewable energies -Stable and controllable energy sources are desirablefrom the standpoint of energy supply.

Extensive distribution

Renewable energy

StableUnstable
Solar heat

Utilization of heat fromtemperature difference

Photovoltaic power
generation

Cooling and heatingby solar heat

- Heat pump use* Difficulty in energy recovery

Biomass (heat/power generation)
Piezoelectric
power generation

Thermionic power generation* Difficulty in energy recovery

Utilization of waste heatfrom factories, etc.

Snow and ice thermalenergy storage
Hot spring power
generation/heat utilization
Geothermal power
generation
Ocean thermalenergy conversion

Wind power generation
Backup generation resources for
power regulation are necessary forhigher introduction of unstable energy
sources → leading to a cost increase.

Small and mediumhydropower generation
Uneven distribution＞

Wave activatedpower generation

Tidal power generation
Ocean current power
generation<Other items to be considered>・ Initial cost, cost recovery
period・ Maximum output, energy
density・ Energy recovery and delivery
・ Operational management,
reliability, etc.

Unused energy○ Temperature differenceenergySewage water, river water,seawater, groundwater, etc.

Case that heat source
temperature does not reacha usable temperature range.

Applicable areas ofheat pumptechnology○ Waste heat energy
Factories, substations,
underground mall, subways,
etc.
○ Waste to energy
Garbage incineration○ Other energies
Snow and ice thermalenergy, ground source heat,etc.
・ Excess waste heat fromCGS

The underlined parts indicate
electrical output.

・ Outputs of photovoltaic power generation (national average utilization rate: 12%) and wind power generation (national average utilization rate:20%) change significantly.
→ These technologies cannot flexibly respond to changes in electricity demand.
→ They should be combined with an appropriate energy storage technology, in order to respond to output changes of renewable energy sourcesthat are beyond regulation capacity on power system side.
Electricity storage technology: Pumped storage power generation has a large capacity and its overall efficiency is about 70%, NaS battery
efficiency is more than 80%, and Li-ION batteries have higher costs.
Thermal storage technology: Overall efficiency of thermal storage tanks is more than 90% in case that the final demand is for heat utilization.
Aquifer thermal energy should be used for long-term utilization.
↑ Heat pump technology and thermal storage technology are compatible with each other.

Figure 4: Worldwide deployment and efficient use of heat pumps- Firstly, consideration should be given to climate conditions and differences in use in respective regionsClimate conditions

・ World’s climatic division and heat pump (HP) technology
Regional division
Regional
Applicable technology
characteristics
Cold region (lowhumidity)

Mainly for heating

Ground source HPs, seawater source
HPs, etc.
Air source HPs for cold region

Mild weather region(high humidity insummer)

It has four seasons
and requires coolingand heating.

Air source inverter HPs
HP thermal storage system for day andnight

Tropical region (highMainly for coolinghumidity/low humidity)

HP thermal storage system for day andnight
Air source (air cooled/water cooled)
HPs+ Highly efficient humidification during heating and dehumidification during coolingaccording to the region→ Reinforcement of building insulation and a better ventilation system are needed.

Outline of respective HP and thermal storage technologies

Heating

Cooling andheating

Clarification of requirements and appropriate system configurations arenecessary for use in each country.

Industrial use

Commercial use

Residential use

Air cooled HP chiller (two-stagecompression, etc.)
Ground source heat brine chiller
Effective intropical region
Air cooled inverter HP chiller
Heat recovery type turbo refrigerator

Air cooled multiple (two-stage compression,
etc.)
Ground source heat brine chiller

Air cooled air conditioner (two-stagecompression, etc.)
Ground source heat air conditioner, HP
heater for panel floor heating

Air cooled inverter HP chiller
Air cooled package multiple air conditioner

Air cooled inverter air conditioner

Cooling

Inverter HP (air cooled/water cooled) chiller Inverter HP (air cooled/water cooled) chiller
High-efficiency turbo refrigerator (efficiency Package multiple (air cooled/water cooled)
air conditioner
improvement by employing water cooledtype)+ thermal storage (effective use of lower
temperature in nighttime)

HP (air cooled/water cooled) chiller
Package multiple (air cooled/water cooled)
air conditioner

Hot water supply
Hot heat

CO2 refrigerant HP for commercial use
HP for high temperature applications (heatmedium, hot air)

CO2 refrigerant HP for residential use
HP water heater

CO2 refrigerant HP for commercial use
Commercial use HP (hot water circulation
type)Figure 5: Monthly average temperature and sewage temperature in each major city of Japan

Changes in sewage temperature in each city
SapporoSendaiTokyo

Niigata

Osaka

Average temperature, maximum temperature andminimum temperature in Tokyo
Kobe

Temperature (℃)

Sewage temperature (℃)

Maximum temperature in Tokyo is not
so much different from that in Osaka.

Minimum temperature of
sewage is much higher.
Jan.

Month

Feb.

Mar.

Maximum
temperature (℃)

Apr.

May

Jun.

Jul.

Averagetemperature (℃)

Sewage temperature in Sapporo is advantageous to obtain heat for heating and hot
water supply in winter as well as heat for cooling in summer.

Aug.

Sep.

Oct.

Nov.

Minimum
temperature (℃)

Dec.

Ebie sewage
treatment area

Example of sewage conduit flow measurement in businessand commercial areas (total floor area of houses occupies
10%)・ Changes in a day are smaller compared to residential
areas.
・ Sewage flow peaks around 11:00 P.M.

Example of sewage conduit flow measurement inresidential areas (total floor area of houses occupies
72%)
・ Sewage flow significantly decreases in early morning.
・ Sewage flow peaks around 9:00 A.M.

Sewage flow (m3/h)

Measurement areas in Osaka-shi

Sewage flow (m3/h)

Figure 6: Characteristics of sewage heat, hourly sewage flow and trend of monthly sewage temperature

Residential andcommercial area

Commercial
area

Residential
area

Tsumori sewage
treatment area

Suminoe sewage
treatment area

Hour (h)Heat utilization potential in Osaka-shi

This shows an
estimated value.

Sewage conduits in Osaka-shi with a heat utilization
potential of 5 GJ/h (more than 1,400 kW)

Hour (h)Figure 7: Various methods for sewage heat utilization
Various methods for sewage heat utilization
Heat source

Heat exchange

Heat exchanger

Heat utilization
methodTreated water

Existing heatexchanger

Plate typeSpiral type
Shell & tube type

Individual use (1:1)

Inside-of-conduit typeheat exchanger

Response tocontaminatedwater(contamination by
biological slime)

District heat supply(1:n)

Outside-of-conduit
type heat exchanger

Response tocontaminatedwater

Heat source water(1:n)

Treated water
Untreated water
Untreated water

Sewage conduit
Sewagetreatment plant

Sewage conduit
Pumping station

Places for sewage heat recovery

Water screen + heat exchanger

Heat
recoveryHeat
recoverySewage heat exchanger

Inside-of-conduit type heat exchange
method for heat from untreated water

Device to prevent foreign matters(screening device)

Outside-of-conduit type heat exchange
method for heat from untreated waterFigure 8: Cases of sewage heat utilization in Japan- Sewage heat utilization in Japan is limited only to sewage treatment plants, pumping stations and surrounding areas -Utilization of treated water as heat source

Large plant
Makuhari Shintoshin area, Shinagawa Sony City, etc.
Shibaura → Sony Shinagawa
at present

Makuhari Shintoshin area

Project for effective use of thearea above Shibaura Water
Reclamation Center with its
reconstruction
Business approval: March 31, 1987
Construction of a 32-story
Start of supply: April 1, 1990
Service district: 1-chome, Nakase, Mihama-ku,
building with a height of about
Chiba-shi, Chiba prefecture and surrounding areas 153 m
Area of the district: 48.9 ha as of March 31, 2008
Total floor area: 919,681 m2 as of March 31, 2008
Buildings receiving heat : Office buildings, hotels

Small plant
Bureau of Sewage, Tokyo
Metropolitan Government (11 plants)

Nagoya City Sewage Bureau (6 plants)

Ochiai

Water reclamation centers in Tokyo
Facility

Start ofoperationAir
conditioning
floor area

OchiaiJan. 1987

2,270 m2

Shingashi

Apr. 1990

2,680 m2

Morigasaki

Apr. 1991

2,490 m2

KosugeApr. 1993

5,910 m2

Kitatama

Apr. 1994

450 m2

NakanoJul. 1995

5,600 m2

AriakeSep. 1995

4,410 m2

Shibaura

Apr. 1997

2,705 m2

Nakagawa

Feb. 2000

4,106 m2

Ukima

Apr. 2001

4,066 m2

Miyagi

Apr. 2005

2,421 m2

Horidome

Meijo

Heat exchanger is a general plate type that does notincorporate any new technological elements of heatexchanger systems.

Utilization of untreated water as heat source

Only two large plants: They are forced to use untreated water because no treated water is available from relay pumping stations.
Installation cost of heat supply conduits is almost
similar to that of heat source equipment.
Koraku 1-chome district

The water treatment plant and heat source plant
are connected by the heat source water conduit
with a length of about 1 km.
West exit area of Morioka station

Nakagawa Pumping Station

Conduit length is about 400 m.

Start of supply: July 1, 1994
Area of the district: 21.6 ha as of March 31, 2008
Total floor area: 294,800 m2 as of March 31,
2008
Sewage water volume: About 50,000 m3/day

The heat exchanger ismade of titanium and astrainer filtrates untreatedwater in conduit.

Start of supply: November 25, 1997
Area of the district: 2.4 ha as of November 30,
2008
Total floor area: 101,900 m2 as of November
30, 2008

The heat exchanger is made ofstainless steel and a strainer filtrates
untreated water in conduit.
The heat exchanger is washedinside by sponge ball.

Figure 9: Large-scale district heating and cooling (DHC) with using treated sewage water as heat sourcein Schlieren, Zurich
・ 30% of the total heat demand in Schlieren district, Zurich are met by using cold heat directly from sewage water and 55% aresupplied by heat pumps using sewage water heat. As a result, fossil fuels are used for meeting only 15% of the total heat
demand in this district.
・ Limmat river in Zurich also serves as a heat source for district heating and cooling.
Schlieren district in Zurich: DHC with using sewage water heat
Energy center
Sewage conduit

Energy center

Heat supply pipe

Equipment capacity
Heating by heat pumps: 11,100 kW, cooling by heatpumps: 9,000 kW
Gas boiler: 17,000 kW

Figure 10: District heat supply with hybrid heat source of sewage water and seawater in Helsinki
・ By switching heat source water from treated sewage water to seawater between winter and summer, the heat pumps aim at
ensuring their heat source capacity and improving their efficiency.

Seawater
Sewage water heat(treated water)

Technical data:
5 units of heat pumps (Friotherm’s Unitop®
50FY)
Operation in winterHeating capacity: 16,770 kW
Supply water volume: 1,221 m3/h
Return temperature/feed temperature:
50/62℃
Electricity usage: 4,770 kW
Electric motor capacity: 6,500 kW
Cooling capacity: 12,000 kW
Inlet temperature and outlet temperatureof sewage water: 10/4℃
Operation in summer
Heating capacity: 18,113 kW
Supply water volume: 370 m3/h
Return temperature/feed temperature:
45/88℃
Electricity usage: 6,113 kW
Cooling capacity: 12,000 kW
Inlet temperature and outlet temperature
for DHC: 20/4℃

Figure 11: System for variable temperature district heat supply in winter/heat source water supply insummer in Limmatfeld, Zurich・ Though this district heat supply system was built with expecting that heat loss during conveyance would be smaller as the heat source is relatively close
to the place of heat demand, it is a highly advanced system that significantly improves the performance of buildings and secondary side air conditioning
equipment and changes supply temperature according to outdoor temperature (air-conditioning load).
・ It is said that dissemination of district heat supply systems remains low and one possible reason is that inflexible system operation leads to loss ofopportunities to save energy.

Multiple-family dwellings
are steadily developed
year-by-year.

EKZ’s office

New housing development project isplanned near EKZ’s office.

System control and charging are
entirely conducted online.

Systems on housing side

Heat source system

Radiant panels are employed for terminal
equipment as they can provide heating at a
low temperature.
Hot water can be produced by using water
for heating in winter.
Hot water can be produced while providing
radiation cooling in summer.

4 units of heat source
HP with a capacity of
1,000 kW

Conventional heatsourceHeat source pipes
Heat source equipment
are directly buried.
room
Significant energy savings are expected
as supply temperature is variable.

HP heat source from sewage water heat
(during heating)
Bypass operation in summer

Figure 12: Athletes’ village in Whistler - network to supply treated sewage water as heat source
・ The network recovers sewage water heat to supply heat source water with a temperature of 10 to 15℃ which is used as heat source for heat pumps.
The temperature of the returned water from the heat pumps ranges from 6 to 10℃. 300 units of heat pumps in the first phase and 600 units in thesecond phase will be connected with low temperature heat supply pipes.
・ If energy density in the supply area drops, the loss of heat would become large in case of high temperature heat supply. In this example, efficiency isimproved by using a relatively low temperature heat source. The network consists of sewage heat utilization systems with a total capacity of 2.5 MW
and heat conduits with a length of 2 km.

Heat pump(individual building)Waste water
treatment facility

Heatexchange

エネルギーコスト(＄/MW)

It is not always appropriate to supply a high-temperature heat.

エネルギー密度(GJ/ha)

Figure 13: Heat source water network system and untreated sewage water heat system in Bern
・ The needs for heat supply is large even in an area with low energy density. Though we usually use air cooled heat pumps that are operable even in below zeroconditions in Japan, it seems that such heat pumps are not an option in Europe.
・ Generally, water cooled heat pumps cannot be used in below zero conditions. In Europe, there exist systems that use clear water with a temperature of 7-15℃ asheat source.
・ The left figure in this slide shows a low temperature heat supply line which conducts heat exchange with the treated water from a sewage treatment plant (called“ARA” in Germany and Switzerland). This temperature range allows to bury pipes directly in the ground and no insulation is necessary. Cost reduction is alsoachieved.
・ On the other hand, the system in Gäbelbach conducts heat exchange in the middle of pumping sewage water to main sewage conduits on the hill from thepumping station at the bottom of the valley.
Bremgarten district in Bern: Low temperature heat source water line

Gäbelbach district in Bern: Heat recovery from sewage supply pipes

Pumping station at thebottom of the valley

Heat source
water pipe

Equipment room in
multiple-family dwelling

Sewagetreatment plant: Customer
This line consists of low temperature heat source water line to conduct heat exchange with theeffluent from ARA (sewage treatment plant). Nearby houses and offices have their own heatpumps.
2 units of heat exchangers with a capacity of 700 kW, 13℃/9℃ for feed temperature and11℃/7℃ for return temperature
Conduit length: 3,750 m + 800 m, 477 m + 550 m +73 m

Double pipe sewage heat exchangers and heat pumps are installed in
the equipment room of the multiple-family dwelling. The pipes for heatexchangers have the same diameter of water supply pipes. After heatexchange, garbage flows with sewage.

Figure 14: Advanced heat source water network system in Adliswil, Zurich・ This slide shows the advanced heat source water network type sewage heat utilization system operated by EKZ in central
Switzerland.
・ The heat source water network was employed with consideration given to the distance to the load center in this case.

Supply area
Sewagetreatment plant

・ They said that the heat
・ The plate type heat exchanger responds toexchanger is cleaned by
the load of about 1,000 kW at present.
circulating hydrogen
・ They said that if the load increases,
peroxide once a week.
additional heat exchanger will be installed.
・ If operation of a plate typeheat exchanger is realized,
high efficiency can beachieved with lower cost.

Heat source
water pipe

This network system consists of low temperature
heat source water line to conduct heat exchangewith the effluent from ARA (sewage treatment
plant).
Capacity of heat exchanger on sewage treatment
plant side: 2,800 kW
Capacity of heat pumps in each district: 140 kW +1,060 kW + 1,730 kW + 700 kW: Customer

Only the circulation pumpand heat exchanger are
installed in this building.

Heat pumps for heating on
housing side

Figure 15: Outline of overseas survey as part of NEDO Sewage Heat Research
In starting the NEDO research, the situation of sewage heat utilization is researched on the Internet.
→ We found the existence of a heat recovery system with using heat exchangers directly installed in sewage conduit.
→ We made contact with professor Thielen of University of Applied Sciences Giessen-Friedberg, who is a leading expert in Germany.
In September 2010, we participated in the 4th Conference of Sewage Heat Utilization in Bochum, Germany (Nakaso and Mike of Sogo Setsubi Consulting Co., Ltd.)→ We visited the sewage heat utilization system in Bochum and found the existence of the association InfraWatt in Switzerland.
→ In January 2011, we visited professor Thielen at the university.
→ We visited the association InfraWatt (Raiser Technical Office) in Bern, ARA Bern and others.
→ We visited Picatech Huber AG in Luzern (professor Nakao and Nakaso).
→ In September 2011, we visited the association InfraWatt (national organization) and EKZ (electric utility) in Zurich (Professor Nakao and Nakaso), together with officialsof MLIT.
→ We presented our activities (the government and NEDO) at the 5th Conference of Sewage Heat Utilization in Berlin.
→ We visited IKEA shopping center and other three facilities in Berlin, Berlin City Waterworks and Sewage Bureau and the Federal Ministry for Environment,
Nature Protection and Nuclear Safety.
Inside-of-conduit typeNew-pipe-installation typeInstallation-in-the-existing-pipe type

Example of heat source system

Cases in Germany: More than 30 cases oftreated water/untreated water utilization
Outside-of-conduit type
Legend: Energy source○ Untreated water (conduit)□ Treated water
Energy utilization form
■ Heating■ Heating and hot water supply■ Cooling, heating and hot watersupplySites under consideration★ Field survey and project inprogress

Cases in Switzerland: More than 80 cases oftreated water/untreated water utilization

Various types are available.

Figure 16: Study tour at various facilities during the Conference of Sewage Heat Utilization in Berlin・ Case of IKEA shopping center in Lichtenberg, Berlin
Inner pipe: 700 mmΦ
Outer pipe: 800 mmΦ

Total length of pipes:
100 m x 2

Double pipe heatexchanger
Water collection installed here
station

IKEA
Equipment room
Conduit gradient 2/100

P

Pressure pipe:
1,000 mmΦ・ The type of the system is similar to that of our system in
Koraku. However, this type has very simple heatexchangers and there is no need to dispose of garbage
in sewage.
・ According to Berlin city sewage authority, there are many
similar water collection stations in Berlin as the city has
many flatlands. They said that they accept the increased
power for water supply pumps at present.

・ Case of fitness center in Friedrichshain-Kreuzberg, Berlin・ High efficiency heat exchange system made by Huber・ Equipment room on the right figure was replaced with the container.

Figure 17: Forms of sewage heat utilization
Individual heatsourceTreatedwater

Tokyo:
Tokyo:
Nagoya:In sewage treatment plant
Shinagawa Sony City
In sewage treatment plant

Easy to handle
Close to sewage
treatment plant

Heat source water
NW

District heat
supplySwitzerland: Bremgarten in Bern, Adliswil in
ZurichFinland:Helsinki
Canada:Athletes’ village in Whistler

Chiba:
Makuhari Shintoshin area
Switzerland: Schlieren and ☆ Limmatfeld in
ZurichGermany:

RawsewageDifficult to handle
Available anywhere

Bochum heated pool
Leverkusen
Berlin IKEA SC
Berlin Friedrichshain
Federal Ministry for
Environment, Nature
Protection and Nuclear Safety
in Berlin
Switzerland: Gäbelbach＋
Installation of
inside-of-conduit
type heat exchanger

Building
loadTokyo: Koraku 1-chome district
Iwate: West exit area of Morioka station

Building
load

Building
load

Building
load

Building
load

Building
load

Building
load

Heat
pump

Heat pump

Heat pumpOr
Installation ofoutside-of-conduit
type heat exchanger

FeatureSewage heatsourceSewage heatsourceSewage heatsourceProduce heat individually for use.

Share one heat source.

Produce heat in bulk for distribution.

One-to-one basis
First-come-first-served basis
Minimum loss
Highly flexible
Small aggregation effectLess economic efficiency if the number ofheat users is large

One-to-N basis
Equal opportunity
Small loss if supply area is extensive
Highly expandable

One-to-N basis
Equal opportunity
Large loss if supply area is extensive
Large-scale
Large aggregation effectLess flexible

Figure 18: Outline of NEDO’s demonstration test equipment
Hot heat utilization facility

Exhaust heat facility

Hot water tank
Cooling
tower
HP water heater

Hot heat utilization facility
Along with sewer
pipe restoration

Heat delivery test
equipment

Tests were conducted at Chishima Sewage
Treatment Plant in Taisho-ku, Osaka-shi to measureseasonal COPs and SCOPs.

Virtual data
centerResearchbuildingIndoorequipment
Outside-ofconduit type(made of resin& aluminum)

Outside-ofconduit type(made of resin& aluminum)

Water
cooledunit

Outside-ofconduit type
(falling liquidfilm)

Sewage feed-in(untreated water)

Makeup water
Outside-of-conduit
type (resin pipe)
Balancingtank

ScreenAppearance of falling liquid film heat exchanger
that delivered the best performance among thedeveloped products and changes in heattransfer property

Catch-basin

Balancingtank

Air cooled
HP chiller
Low constanttemperature water
circulation device

After-fitting type(protected by resin
mortar)Heat source
water
Metal exposure type

Water
discharge

Heat exchanger pipe:
1,200 ΦOverall heat transfer coefficient (w/m2k)

Outside-of-conduit typeheat exchanger
Inside-of-conduit typeheat exchanger

ScreenSewage flow

Heat pump
Sewage flow time (h)SewageFigure 19: Newly developed heat exchangers
・ Newly developed heat exchangers are as follows. As for outside-of-conduit type, falling liquid film heat exchangers have higher
initial performance, reduce performance deterioration caused by biofilm, and become more excellent in performance recovery by
washing.
・ As for inside-of-conduit type, installation-at-conduit-bottom type (parallel type) equipment have a higher overall heat transfer
coefficient and serial type equipment require no header pipe, leading to a cost advantage if their configuration is small.
Category

Outside-of-conduit typeHeat exchanger type

Inside-of-conduit type

Resin + aluminum

Falling liquid film typeDouble pipe typeHeat source water side: 0.25
m/s
Sewage side: 0.10 m/s

Heat source water side: 2.7
m/s
Sewage side: 0.52 kg (m/s)

Heat source water side: 0.75m/s
Sewage side: 1.0 m/s

Installation-at-conduit-bottom
type

Integrated-with-conduit type(resin)Sewage flow velocity: 0.3 m/s
Heat source water flow velocity:

Heat source water side:
0.24 m/s
Sewage side: 0.13 m/s

Photo of appearance

Heat source
water

Flow velocity

Overall heattransfer coefficient(W/m2・k)SewageStainless steel pipe Cooling water

2.8 m/s forparallel type

1.4 m/s forserial type

Connect heat transfer
panels by reverse
return pipes.

Type that installs heattransfer pipes along
inside sewage
conduits in a back andforth manner.

Sewage

①

180

2,000

800

Parallel type
850

Serial type
800

120

②

120

1,300 (after 120 h)

350 (after 120 h)

350

280

100

③

180

1,700

650

600

400

－

Washing method

Water spray flow rate: 0.52
(L/min・m) per unit pipe length

Washing by sewage water at
a flow rate of 1.0 kg/(m・s) for
three minutes.

Washing by industrial waterat a flow rate of 1.5 kg/(m・s)for five minutes.

Increase the flow rate to 0.9
m/s for about one minute.

No washing

Definition of heattransfer area for heattransfer coefficientStandard for outer diameter ofheat exchanger coil (contact
surface with sewage)

Standard for outer diameter ofheat transfer pipe for heatsource water (contact surface
with sewage)

Standard for inner diameterof sewage pipe (contact
surface with sewage)

Contact surface of heatexchanger with sewage (upper
half of outer diameter)

Contact surface withsewage at rib where heatsource water flows① Initial performance② After biofilm
growth③ After washingFigure 20: Newly developed pumping screen
・ The screening device in combination with an outside-of-conduit type heat exchanger has achieved a significant cost reduction
compared to the existing devices made in other countries, by capturing and releasing foreign matters in conduit, as shown below.
・ Mobile type hydraulic spray shows the highest performance. However, comparison of the installation cost of rotary rake type andothers is necessary depending on the volume of water recovered and manhole shape at design stage.
Scraping by electric motor rotary rake

Scraping by electric motor rotary rake

Water intake
screenPerforated metal with 3 mm diameterholes at the bottom

Vertical slit with 2.5 mm diameter holes
at the bottom

Horizontal slit with 2.5 mm diameterholes on the lateral side

Horizontal slit with 2.5 mm diameterholes on the lateral side・ Water intake capacity = 14 L/s (water
depth: 14 cm)
・ Minimum manhole width = 600 mm forpump and pipe space (depending on
main pipe diameter) + main pipe
diameter・ Water intake capacity = 50 L/s(manhole water depth: 19 cm, length:
55 cm)
・ Minimum manhole width = 600 mm for
speed reducer space (depending on
main pipe diameter) + main pipe
diameter + margin on one side・ Water intake capacity = 14 L/s (water
depth: 11 cm)
・ Minimum manhole width = 500 mm forscreen installation width + main
sewage pipe diameter + margin on
one side・ Installation height = pipe elevation

・ Water intake capacity = 10 L/s (water
depth: 9 cm)
・ Minimum manhole width = 500 mm forequipment installation width + main
sewage pipe diameter + margin on
one side・ Screen installation height = pipe
elevation (integrated pump height =pipe elevation - 50 mm)

500 households

More than 1,900 households

500 households

350 households

Application

Hot water
supply load*

Equipment
appearance

Manhole inner diameter:
1,200 mm600

Scraping by electric motor rotary rake

227

Mobile type hydraulic spray

600

Washing
methodManhole inner diameter:
1,500 mm552

Manhole inner diameter2.0 x 3.0

Manhole innerdiameter:
1,500 mm

Structuredescription

Spray water from nozzle moving to thedirection of pipe axis blows foreign
matters in perforated metal holes to flow
with sewage.

Rakes at the pipe bottom remove foreign
matters during water recovery.

Horizontally rotating rakes remove
foreign matters from the fixed screen
plate slit during water recovery.

Horizontally rotating rakes remove
foreign matters from the fixed screen
plate slit and the pumps integrated withmain equipment recover water.

Installability
andmaintainability

・ Installation in a dried condition (oneday installation)
・ There exists a risk of corrosion andshortening life of submerged hydrauliccylinders・ Washer spray should not be usedduring the inspection in manhole.

・ Installation in a dried condition (oneday installation)
・ The fluid flows right above the rakes,
resulting in a large risk of damaging
rake tine or slit.
・ Inspection work can be conductedduring water recovery.

・ Installation and inspection work can be
conducted while allowing the water toflow on one side (one day installation).
・ If the captured foreign matters are
dried, they cause the damage of rotaryrakes.

・ Installation and inspection work can be
conducted while allowing the water toflow on one side (one day installation).
・ As the removed foreign matters areaccumulated, it prevents rake tine frommoving or causes deformation.

◎: Highly effective to remove foreign
matter and possible to recover thewater stably.

△: Applicable to a system that allows
foreign matters to flow into heatexchangers.

△: Low failure risk as it is an applied
form of ready-made products.
Foreign matters including fibers, etc.
are easy to pass through.

△: Compared to other equipment, alarger space for installation isrequired to recover an equivalentamount of water.

Evaluation＊ This is the case that heat pumps operate for eight hours in midnight in a multiple-family dwelling (temperature difference of sewage water is 5 K). The figures in the table become 2.5 times
larger in case of 20 hour operation per day.