Note: Descriptions are shown in the official language in which they were submitted.
. WO 93/07424 212 0 S 2 6 PCT/A~92~00125
--1--
System for Recovering Heat from Waste Water
The invention pertains to a system for recovering heat ~rom
waste water which arises, preferably discontînuously, from,
in particular, households, houses, commercial ente ~ rise~,
etc., which include~ at least ~ counter-flow heat exchanger
~hrough which the waste water flows, and which is con~ected
in the circuit of at least one warm water reservoir or a
water hea~er.
Such sy~tems for recovering heat from waste water are
generally known.
It is th~ object of the i~vention to further develop such
3y8tems such that they are enabled to process all h~usehold-
conventional waste watérs in chemically and mechanically
clean or s~lightly soiled form a~ well as in strongly soiled
orm, i.e. when soap,~ grease, hairs, detergent~, chemical
~: ~ clean~ers~ ood leftovers, etc. are contained in the waste
wat r. Further~or~, uch:a system should operate fully
aut~matically, ~hould be largely m~intenance-fr~e, it should
~ be~prQvldcd~in a~structurally simple apparatus with a
:~ : 20~ buil*-in unit:concept,~and~t should have a degree of
efficiency as~ high as possible.
; These ob~ects are ~ttained, in accordance with the
invention, with~a~system of:the foregoing kind in that a
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. . Wo 93/07424 PCT~AT92/00125
-2- 2120~26
~ensor i~ provided in the discharge line for the waste water
which is responsive to incoming waste water, which sensor is
connected to at least one pump or to a control device
controlling the pump(s), with which waste water is drawn off
when the pump is turned on upon the occurrence of a signal
indicating ~urther waste water in the waste wate~r_line~which
is then guided or pumped through the heat exchang~r.
In a preferred embodiment it is envisioned that tempera~ure
sensors are provided for determining the temperature o~ the
waste water and the storage water flowing into and from th~
heat exchanger~ particularly in the immediate vicinity of
~he corresponding connections of the heat exchanger, which
tempera~ure sensor~ are connected to the control device,
with which the amount of the velocity o~ throughput of.the
pump and/or the pumping amount of the pump in the loop *or
the storage water can be controlled in dependence of the
measur~d:or calculated te~perature diference between th~
inlet at the heat exchanger for the waste water and the
~:~ outlet ~or ~he ~torage water and/or at the inlet for the
s~orag~ water:and at the o~tlet for the waste water~
A fuxther ad~antageous embodiment is characterized in that a
: ~ pipe~ection orlan a~sembly unit i~ pr~vided ~or connection
in~a co~ventional waste water line in which the waste water
~` sensor(~) are disposed and with which the intake line of the
pump or the waste wa er outlet line (downstream) of the Xeat
ex~hanger communicate.
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'W0 93/07424 212 0 5 26 PCT/AT92/00125
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With the sensor which registers the occurrence o~ water, the
pump is always turned on when waste water is available for
processing; when the water ~tops, the pump is turned offO
Due to the controlled supply of the warm waste water and the
controlled ~upply of the stora~e water to be heat~d to the
heat exchanger, optimized heat exchange is enabled, so that
~he heat content o~ the waste water can be optimally
utilized. Finally, the ~y~tem can be delivered in the form
o a compact unit, which is aonnected between a water heater
and a waste water line which is easily connected into the
waste water pipe~
.
Pr~ferrad embodiments can be found in the following
description, in the drawing and in the patent claim~.
The drawin~ depiots a schematic CQnstruction of the syst~m
according to ~he invehtion.
he system a~cording to the invention is essentially divid~d
into~th~ee~individual ~omponents, namely a wat~r haater 17,
a main:unit,;which is schematically re~erenced at 18, and
tie-in unit~10~
20~ : The water haater 17 inaludes a cold water supply line 19 and
a: line~ 10 le~ding the a user. An arbitrary heating de~ice,
or instance~electrical heating rods, are indicated at 2~ in
the upper~region of the watér hPater. ~he feed to the line
20 leading to ~he users is effected via a motor mixer 70 ts
:~:
:
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which a hot water conducting line 22 and a line 23
conducting water heated by the waste water. The temperature
in the line 20 is sensed by means of a temperature probe S
and it is evaluated with a control de~ice or a control
compu~er 8; the motor mixer 7 is also controlled~wi~h the
control device 8.
A further essential device is the tie-in unit 10 which can
be inserted into any arbitrary waste water pipe or a w~ste
water line and which has a corresponding cross-section
adapted to that of the non-illustrated was~e water line. The
main unit 18 includes as essential components the control
unit 8, a cyclone 2, a pump 1, a heat exchanger 3, a further
: pump 4 and possibly a check val~e 9.
The ~ie-in unit 10 has a downwardly directed recess or a
:: bulge 26, into which a suction pipe ~1 opens which leads to
the pump lr q~he bulge ~6 :is closed off on top with a filter
or: a filter si~ve 15;: so that waste water entering the
tie-in unlit ~lO: ~lows through the filter 15 in orde~ to reach
the suction opening OI the line 11 and it is prsfiltere~ in
tha~way. ~ctually, the~lines, sensors and components whi h
form the~tie-in~}unit:lO could aiso be formed or disposed in
a~waste wa~er line. ~: ~
:: ~ : :
The warm waste water aspirated by the pump 1 is supplied_
.into the cyclon 2 in which a float 12 is disposed which
aarries a rod 27 at its upper side, with which a ventilation
'WO 93/07424 2 1 2 0 5 2 ~ Pc~/AT92/ool25
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flap 13 for a ventilation line 16 can be adjusted. Dep~nding
on the amount of air aspirated with the waste water in the
line 11, the water level 28 in the cyclone 2 rises or falls;
while the water level 18 rises, the ventilation flap 13 is
closed; when the flap 13 is open, air is fed bac~ via the
line 16 to the tia-in unit 10, i.e. to a location upstream
of the suction line 11, so as to maintain the incoming waste
water at temperature by means of the v~ry warm air and so as
not to waste the heat content in the air. ~he pres~ure of
the waste water in the cyclone s~parator 2 is controlled
with the float -12 and the ventilation ~lap 13, whiah waste
water is fed through a line 29 to a corresponding ~upply
connector 30 in~o the heat exchanger 3 and w~ich leaves the
~heat exchang~r at 31 through the line 14. The line 14 issues
into th~ ti~-in unit downstream of the filter 15; it is
pos8ible to proYide a pipe 32 in order to introdu~e the
returning,~cooled~waste water into the tie-in unit as far
from the suction line 11 as possible, and to prevent a~y
: back~low.
0:~ ~h~ heat exah~nger~is~further supplied with cool water at a
supply~openin~ 32, which water is withdrawn from the lower
part Qf:~the wat~r:heater 17, or'with cold~water from the
line 19 Yia a pump 4~ Tha~ water which ~lows ~hrough the
heat: exchanger lea~es the same at the ou~let opening 33 and
:: : ~ `: : :
it reaches the upper part of the water heater ~7 through_a
: lin~25 and: the cheok valve 9, whereby a stra~i~ication of
W0 93/07424 212 0 5 2 ~ PCT~AT92~00125
the water forms in the water heater 17 according to its
temperature.
In accordance with the withdrawal of warmed water ~rom the
water heater 17 through the line 20, cold water ~an flow in
through the cold water line 19 into the heat exchanger 3 or
into the water heater 17, i.e. into its lower part~
The control device 8 is connected to water sensors 6, to
temperature sensors 5 and to the pumps 1 and 4O ~he water
sensor 6 ups~ream of the suction line 11 serves to detect
incoming waste water and, upon receiving a corresponding
signal from the senso~, the control device 8 places the pump
1 into operation for drawing off the available waste water.
: The temperatur~ o~ the waste water is simultane~usly
measured with ~he appropriate temperatur~ probe 5.
A water ~eel~r 6' is disposed downstream o~ the suction line
11 with whiah it is det~rmined whether waste water ha~
:
: tr~v~rsed ~cros~ the filt~r 15 while the pump 1 operated; if
:~ this is affirmatîve~ it is an indiaation that the filter 15
is plugged up~ In that case, the control device 8 re~erses
.
~1 20~ ~he:pumpi~g direction o~ the pump 1 and pushes already
:
aspirated water through the line 11 into the ~ulgQ 26 and
thereby flushes the:filter 15 counter tv its filtering
direct~ion~ so as to provide free passage for the waste water
in_o t~e bulge 26 for aspiration through the line 11; the
flushing is maintained for a period of time, so as to allow
WO 93/07424 212 0 5 ~ 6 PCT/~T92/00125
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the f lushed~out dirt to be removed, th t is to say that
after the flushing, waste water is not immediately aspirated
again, but instead it is used for removing the flushed-out
dirt .
The control device further monitors the temperatures ~t the
inlets 30 and 32 of the heat exchanger 3 and/or at its
outlets 31 and 33. The control device forms the difference
of the temperature values at the heat exchanger ~r D~ean~; of
appropriate calculation units, i.e. the difference at the
10 inlet 30 for the waste water and at the outlet 33 ~or warm
water and/or th difference at the outlet 31 for waste water
and at th~ inl~t 32 for cold water from the water heater 1
:: or the cold water line 19.
ne te~pe~ature dif ~Eerentials ~T at the respecti~e inlet~;
~nd outIets is a measure for the heat krans~er from the warm
waste w~te:r to the cool wate:r 8upplied from the water heater
17 or ~Erom t:he cold water li~ 19. The tem~eratuxe
diffe~en~ials ~thus d~termined are preferably maintained
equal; ~or~ ~hat purpose: it i5. provided that khe am~:sunt of
20: warm waste water and the amount of ool water fl~ing
througlh the water heater~correspond to ona another in terms
: o~ volume. The~cor~esponding volumes aan be adjusted by
controlling he pump~1 and/or the pump 4, in that ths
: ~ throughp~t o~ the wasta water and/or of t~ cool water is
regulate~, *or the purpose o~ mutually adjusting th~ amounts
of water circulating through the heat exchang~r in ~he
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respecti~e divisions for waste water and for cc)ld water per
unit time.
The measurement of the 1:emperature dif ferences ~T is
pra::tically done with t:wo differential controllers, for
instance with PID properties, whose voltage values are
processed by the control device 8.
The tie-in unit 10 se~fes several functions; it serves to
withdraw the wa~:te water flowing in the discharge pipelines,
as we~l as the back~eed thereo~ after the heat exchange
10 proc:ess~; furthe~ore, the air is disposed of through this
c:onnector segment 10 which had been aspiral~ed.
Nagnetically inductive sensors may be provided fc3r detecting
.
wat~r supply ~and the water temperatures.
q~he dimensions of the entire tie-in unit 10 are aimed at a
imple assQmbly into,existing discharge pipes; the maximum
built-in depth ~below the discharge level, :IEor instanGe, iE;
about 2 cm; connec~tor~ are pro~ided in the tie-in unit for
th~ entry of~ wasts water:, for the diss:~h~rge o:E waste water,
Eor~ a æuc~ion cc::nnection to the`main unit, and for a water
rel:urn a~ r the heat exchang~ proces~; as well a~ ~or an air
return~
The main unit 18 can be conf igllred as a built-in uLnit, so
that an unproblematic: assembly into, for instance, kitchen
,
,
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_ g _
cabinets below an exist'ng counter is enabled; the housing
measurements correspond *o the usual norm for household
appliances o~ ~0 x 60 cm and are easily attained. The main
unit 18 also allows for the necessary operational management
which is required in order to withdraw a maximum in heat
energy from the soiled waste water and thus to warm up the
cold fresh water.
The assembled system components are acoustically dampened
and built into th~ main unit; connectors exist compatibls
with the tie-in unit~ -
~he pumps 1 and 4 provided in the ~ain unit 18 can be~orce-feeders and they are pre~erably infinitely ~ariable,
:~ so as to assure corresponding control response.
: :
~rhe water reservoir or water heater 17 is preferable loaded
by the main unit 18 under consideration Qf the heat
strati:fication:~in the: uE~?er third of i*s volume; reheating
with the rsheating deYice 21 is preferably effected in the
~up~er~third o~f the:wa~er heater 17.
For ~ptimizing the~degree~of ef~iciency of the system, the
,
20~ eleotronically controlle~ three-way mixer 7 adjusts the
withdrawal:temp~ra~ure onto a rated value; this concept
leads to ~he ~act tha~, when any arbitrary amount of warm
wa~er is withdrawn ~hro-~gh the line 20, an e~ual amount of
fresh cold water flows into the water heater 17 fro~ below,
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WO 93/07424 212 0 ~ 2 ~pCT/AT92/00125
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which again leads to a cooling of the entire amount of waste
water during ~he heat recovery to the temperature level of
the fresh water and corresponding hea~ recovery.
~hen waste water arriv~s in the tie-in unit 1~, the arrival
is de~ermined by means of the magnetic inductiYe feeler 6
and tha t~mperature is measured with the sensor 5~ From
these measured values the control de~ice 8 in the main unit
18 forms a ~tartoff argumentO In the case of a start, the
entire amount o~ waste water is drawn o~ through the
backflushable ~ilter sieve 15 by means of the pump 1, The
air which i~ necessarily conducted from the disch~rge system
in this proces~ ~s well disturbs for various reasons,
because when the system is at a stillstand this can lead ~o
incrustation fro~ dried dirt. Also, water with detergent
foams vexy sltrongly ~ Iring the wi~hdrawal suation from the
ewer, especially when air is present. A water-air mixture
:
(foam~ ha~; an entirely different specific heat capacity a~
c:c~mpared to wat:er alone,: which would make the control o~ ~he
throughput in the h~at exchan~er 3 or the ~Ere~hwater pu~p 4
very difficult in terms of :a~taining equal flow speeas for
wa~te water and :~Eresh water in the heat exchanger 3O
In order to realize the separation o~ water and air
effQctively,: fast, and withou~ large voIumes of re~;t water
which would ac~ol d~wn during stillstand and thus reduce the
fficiency o~ ~he system, we h~ve E,rovlded the relati~ely
.
::~ small cyclone separator ~ with correspondiny dimen~ions. The
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~W0 93/07424 PCT/AT92~00125
~loat-controlled ventilation or hinged valve 13 leads to a
pressure at the heat exchanger 3 which corresponds ~o the
throughput volume (air and water~ of the pump 1, or to the
water level in the cyclone 2, which conducts the wast~ water
through the w~ste water part of the heat exchanger 3. The
the water level rîses, this is an indication of a flow speed
through the heat exchanger 3 which is too low, so that the
pressuxe in the cyclone 2 should be raised, for which
purpose the ventilation opening of the cyclone 2 is closed
with the flap 13 by means of the rising float 12 7 The water
l~vel could also be measured with the control device 8 and
the air ventilation could be controlled accordingly.
The construction of ~h~ heat exchanger 3 is ~uch that
designed partial turbulences are c~used th~rein ~hich
absolutely prevent ~he deposit of grease and similar
impurities present in the waste water during the cooling
process, even if no grease solven~s are present in the waste
water.
The cooled-down was~e water and the air from ~he v2ntilation
20~ are conduc~ed bac~ to the tie-in unit lO and thus ~o the
sewage; ~yst~m;~air and water are separately conducted so as
not to have to settle for an efficiency loss in ~he case of
a:~mall amoun of waste water per unit time (a lot o~f air is
:~ condu~ted), since the air produced in the ventilation
::~ contains heat which would be los' if it were conduct~d back
~ together with the coolded-down waste water.
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The cleaning of the filter sieve 15 is provided so as to
maintain this filter sieve pervious, which becomes soiled at
variable intervals; bath water hardly soils a filter sieve;
w~hing machine water soils relatively quickly due to the
lînt contained therein. As soon as the filter si~e besomes
impervious to the waste water, the same is bypassed, leading
to the presence of water in the tie-in unit 10 i~mediately
downstream (as seen in the direction of flow) of the filter
sieve 150 The ~urther water det~ctor 6' placed at that
location sends a corresponding signal.to the control device,
which then reverses the pump 1 for a shor time with regard
to i~s-pumping direction and thus effects an extremely
e~fective backflushing of the ~ilter sieve 15, whereby the
bac~lushed water is discharged through the tie-in unit 10
a~d conducted into the sewer~A short st~p of ~he suction,
: i.e. o~ the pump 1, p~ior to a renewed start in the normal
conYey~ ng di~rection of the pump 1 allows the dirt to flow by
the ~iev~ 15 together wi~h the waste water simultaneously
wing through the tie-in un:it 10, which prevents the
:: 20 :~lushed-out impurit~eæ :Erom being re-aspirated right away
~ and~rom plugging the ~ilter 15.
~ . :
T~e total degree of efficiency Of the system in cooperation
wi~h the di~fering and~mu~ually ind:ependent w~rm water
withdrawal ahd discharge amounts occurring in a household,
as-well: as the instants and tim~ intervals thereof, c:an .Q.nly
be optimized when the amount~ of discharg~n~ w~ste water and
freshwater to be heated are adapted to one another, and are
.
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`W0 93/07424 212 ~ 5 2 6 PCT/AT92/00125
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pre~erably equal, since that assures optimal heat tr~nsfer
and optimal heat recovery. In order to fulfill this
re~uirement, the control device measures all temperatures at
the heat exchanger 3, which is operated in counterflow, and
controls the infinitely adjustable pump 1 and/or ,~he pump-4
in a manner such that a preferably equal absolute
temperature differential Q~ results between the measurement
points 30 and 33 for the warm waste water and the warm ~resh
water, as compared to the measurement points 31 and 32 for
the cold waste water and the cold fresh water~
The equilibrium of the amounts of water is attained
virtually perfectly by controlling the flow velocity; the
:~ diameters of the ~ipes and of the heat exchanger are known,
~o that the~flow v~locity (i.e. ~he water pressure3 is the
only par~meter to be controlled.
:
~: The spring-biased check~valve 9 tied into ~he feed line 25
~: to~the water heater, pri~vents an unwanted circulation
through the usable~water~part o~ the syst~m which i~
, ~ : .
connected in ~he by-pass~configuration with the water
20~ heater;~ Guch circulation~would destroy the ~tratification in
: the wat~r:heater ~7:during stil~stand and an unde~ireable
admixing of cold water~duri~g a withdr~wal of warm water.
~arious sie~es or~sieY2 materials may be utilied for the_
~,
filter sieve 17, for instance ~abric sieves with d mesh
width of about lOO:~m.
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