The present invention relates to a method and an apparatus for transferring heat from waste water from a building to service water to the building by utilizing the heat pipe principle.

Heat pipes have been ^' used in many applications. including both cooling and heating. Heat pipes are built up as a closed circulation system, in which -the heat is transported continuously by means of a volatile heat transferring medium from one place, the vaporization place, to another place, the condensation place, in the system. The heat transferring medium is self-circulating; no pump is required. If the condensation place is located at a higher level than the vaporization place, the heat trans¬ port can only take place in one direction, namely from below and ^' upwards.

In the Swedish Patent No. 7613962-5 the use of the heat pipe principle for the recovery of heat in waste water is disclosed. In conformity herewith the present invention relates to a method for transferring heat from the waste water of a building to its incoming service water by means of a heat transferring medium self-circulating in a closed pipe system between a vaporization place, through which the waste water flows, and a condensation place, through which the service water flows and which is located at a higher level than the vaporization place, wherein the transferring medium is vaporized at the vaporization place and flows from this place in vapor phase to the condensa- tion place, is condensed at the condensation place during heat emission for said heat transfer and flows in fluid phase back to the vaporization place.

The present invention is an improvement of such a metho ^^^ξ-^ _,

in order to essentially increase the efficiency of the heat transfer. A number of experiments with different embodiments for utilizing such a method have proved, that the configuration of the vaporization place, i.e. the heat transfer from the waste water, is of particularly importance to the efficiency, and the present invention provides for said purpose a special method for this heat transfer.

In this respect the present invention is characterized by feeding the waste water to the vaporization place where there are substantially undisturbed layer zones compri¬ sing layers of temperature in the waste water with the top layer being warmer than the bottom layer and trans¬ ferring heat from the waste water to the heat transfer¬ ring medium in said layers independent of each other.

Thus, the absorption of heat from the waste water shall according to the invention take place in at least two layers (level zones) . A natural zoning of warm water uppermost and cold water towards the bottom takes place in a vessel, unless flows disturb this zoning. It is accordingly in order to obtain the required zoning essen¬ tial, that such disturbing flows which result in a mi¬ xing of the upper warmer waste water with the lower cold waste water are avoided. The inflow of the waste water must therefor,; according to the invention, take place in such a manner, that the waste water has the possibility to be zoned. The waste water should be fed into the vapo¬ rization place below the level of the waste water therein and in a preferred method, according to the invention, the waste water is for zone-promoting purposes supplied to the vaporization place in a substantially horizontal direction,, wherein moreover the waste water prefe¬ rably is supplied tangentially. Preferably accor- ing to the invention the kinetic energy of the waste water should also be damped immediately before fc-. c.

^{■ < V} V'

or at the intake into the vaporization place.

In a preferred method ^■ according to the invention the heat transfer takes place in each of said zones along a substan¬ tially horizontal plane. The condensate of the heat trans- ferring medium should accumulate covering a relatively large area in said plane so that the vaporization of the heat transferring medium is promoted.

As previously mentioned the present invention also rela¬ tes to an apparatus for carrying out the method. The appa- ratus according to the invention includes a waste water vessel, a service water vessel located at a higher level than the waste water vessel and a self-circulating heat transferring medium in a closed pipe system between said vessels. In order to obtain the above mentioned advan- tageous configuration of the vaporization place, i.e. the waste water vessel, in said purpose to obtain the essentially increased efficiency compared with previous¬ ly known technic, the apparatus according to the inven¬ tion is characterized by layer-promoting means to obtain essentially undisturbed zoning into temperature layers in the waste water vessel with an upper layer zone of warmer waste water than the lower layer zone and at least two separate pipe circuits for the heat transferring medium arranged with the heat-absorbing parts of the pipe cir- cuits in the waste water vessel spaced apart vertically with at least one of said pipe circuit parts in each layer zone.

In a preferred embodiment of the invention said layer- promoting means for the incoming waste water comprises of a tangentially connected inlet pipe, preferably ha¬ ving a channel in the wall of the vessel successively leading into the vessel.

^UP.EX£

O FI ^• WIFO

In another embodiment said layer-promoting means compri¬ ses of a partition wall extending into the waste water vessel substantially horizontally, said wall covering an essential part of the inner area of the vessel. The parti- tion wall is located such that it separates the zones in which the heat absorption to said pipe circuits takes place.

In a preferred embodiment of the invention said heat-ab¬ sorbing pipe circuits in the waste water vessel are for- med as a substantially plane spiral. Such a plane spiral utilizes the pipe length effectively due to the fact that condensate is present in the total pipe length in the spiral.

The invention is in the following described with refe- rence to the accompanying drawings which schematically illustrate the principle for a preferred embodiment of the invention, wherein:

Figure 1 is a vertical section through the preferred embodiment,' and

Figure 2 is a section along II-II in Figure 1.

A waste water vessel 1 is arranged for receiving waste water from a building that has valuable heat content, such as, for example, the discharge from clothes washing machines, dish washing machines, bathrooms and the like. The waste water is conducted into the vessel as shown by the arrow A and is discharged at the bottom of the vessels as shown by the arrow B. The waste water supplied to the vessel through the vertical pipe 2 looses a part of its kinetic energy ^' when it meets the waste water le- vel in the pipe 2 and also by the perpendicular deflec¬ tion to the horizontal in tangential inlet 3. Hereby, the

waste water can after entering vessel 1 be zoned so that waste water that is warmer than that inside the inlet 3 rises on entering the vessel and colder waste water sinks downward, and this takes place without disturbing the zoning. In the upper warmer layer or zone as well as in the lower colder zone, heat pipe loops 4a and 4b ₇ respectively, are each arranged in a substantially horizontal plane. The pipe loops are preferably formed as a substantially plane spiral.

The outlet for the waste water may preferably be formed as a level-maintaining device and such a device is shown in Figure 1 as an Outle pipe 5 having the outlet ope¬ ning positioned at a desired level in the waste water vessel . A wall or pipe 6 shields the outlet opening of the pipe 5 so that only the colder bottom water flows to the outlet.

An ^' upper vessel 7 is positioned at a higher level above ^' the waste water vessel 1. Heat from the warm waste water flowing through the waste water vessel shall be trans¬ ferred to the contents of vessel 7. Vessel 7 can for in¬ stance be a water heater or the contents of the vessel can be fresh water coming into the building, the fresh water of which shall be pre-heated. The fresh water en¬ ters the vessel at the bottom as shown by the arrow C and is discharged at the top as shown by the arrow D. The heat pipe loops 4a, 4b in the waste water vessel are con¬ nected to screw-line-formed loops 8a, 8b in the fresh water vessel.

Distilled water,, freon, ammonia or like liquids having high vaporization heat are used as heat transferring me¬ dium in these heat pipe loops. The amount of medium is adapted such that optimum heat transfer effect is ob¬ tained. The air is evacuated so that only the pressure of the heat transferring medium in the pipe is present

OMFI _

for the respective temperature. The pipes should be made of metal, for instance copper.