Technical field

The application relates generally to a heat recovery unit. Background Along with residential wastewaters (greywater) down the drain disappear enormous amounts of thermal energy that people have paid for, e.g. when taking a shower.

There have been efforts to utilize the thermal energy of wastewater, e.g. for heating domestic cold water coming to water and shower faucets. When the cold water is supplied with thermal energy from wastewater, there will be less demand for water heated with purchased energy. Using smaller amounts of purchased energy represents a direct saving for the water consumer with no need to use expensive purchased energy for the heating of cold water.

One solution for exploiting the thermal energy of wastewaters is a so-called copper pipe principle, wherein the cold water pipe arriving at a faucet has been wrapped around a drainpipe, the cold water flowing in the copper pipe being heated by wastewater flowing in the drainpipe.

Another solution is to extract the thermal energy from wastewater prior to its entry into a drainpipe. In connection with a shower is installed a heat recovery device (HR device), wherein the cold domestic water is heated by the warm shower water in a free-flowing manner and the preheated water is conducted into a hot water storage tank.

A problem with the currently available devices is a poor efficiency thereof by having a capacity of recovering not more than about 40% of the thermal ener- gy stored in wastewater.

A further problem is that the devices are unreliable in operation with dirt, e.g. hair, skin and sand, which clog the devices, drifting therein along with shower water. In addition, the efficiency of a device is impaired by dirt clinging to the copper pipe surface. Summary

It is one objective of the invention to eliminate some of the prior art problems and to introduce a heat recovery unit with an improved efficiency as well as prolonged maintenance interval and service life. The one objective of the invention is attained with a heat recovery unit of claim 1 .

The heat recovery unit according to one embodiment comprises a heat exchanger for heating incoming domestic water with outgoing water, a pump for pumping the outgoing water through the heat exchanger, and a bypass conduit for directing some of the outgoing water past the heat exchanger. The unit further comprises a filter unit, which has a filter for purifying the outgoing water proceeding to the heat exchanger, and the bypass conduit is connected to the filter unit so as to enable at least some of the water flowing through the filter to be discharged from the filter unit into the bypass conduit. Other embodiments are presented in the dependent claims.

Brief description of the figures

Embodiments of the invention will be described more precisely in a detailed specification of the figures, in which figs. 1 a-1 c show a heat recovery unit in a view of principle and at various viewing angles, and

figs. 2a-2e show details of a filter unit in various embodiments.

Detailed description of the figures

In figs. 1 a and 1 b is shown the construction of a heat recovery unit (HR unit) 100. With the unit 100, the outgoing water, coming e.g. from a shower or else- where, can be used for preheating the cold domestic water coming to the shower faucet or other liquid, e.g. a heat transfer fluid used by a heat transfer fluid exploiting device, prior to its entry into a sewer, a collector, or other service. Alternatively, the unit 100 can be used e.g. in connection with a kitchen or wc faucet, in washing machines, process equipment, and other such devices, which are used for treating a liquid or a material other than solid.

The unit 100 includes a heat exchanger 1 10, e.g. a plate heat exchanger or a copper coil heat exchanger, across which passes the cold domestic water, which arrives along a channel (pipe) 102, e.g. a cold water pipe extending to a shower faucet, and which is preheated in the exchanger 1 10. The preheated domestic water discharges from the exchanger 1 10 along a conduit (pipe) 104 to the shower faucet. The exchanger 1 10 can be e.g. a double-wall plate heat exchanger. The double wall is used for disallowing the blending of liquids with each other in the exchanger 1 10 in the event of a possible leak. Hence, the pure water does not have e.g. wastewater admixed therewith in the occurrence of a leak.

In addition, the unit 100 comprises a pump 120 and a filter unit 130 which in- eludes a filter 132 for cleaning the outgoing water of e.g. dirt, hair and sand present therein, which would obstruct the exchanger 1 10 thereby undermining its efficiency and operating reliability, as well as reducing its longevity and maintenance interval.

The warm outgoing water, which arrives along a conduit (pipe) 122, is pumped by the pump 120 through the unit 130 and the exchanger 1 10 so as to enable the warm outgoing water to be used for preheating the cold domestic water in the exchanger 1 10. The cooled outgoing water used for preheating is discharged from the exchanger 1 10 along a conduit (pipe) 106.

The unit 130 has connected therewith or includes an inlet conduit (pipe, fitting) 128, which allows a flow of outgoing water from the pump 120 to the unit 130. In addition, the unit 130 has connected therewith or includes an outlet conduit (pipe, fitting) 134, which allows a flow of at least some of the outgoing water from the unit 130 to the exchanger 1 10.

The unit 1 10 further comprises a bypass conduit 140 connected to the filter unit 130 by means of a conduit (pipe, fitting) 138 so as to enable at least a portion - if necessary, even all - of the outgoing water passing through the filter unit 130 to be conducted past the heat exchanger 1 10. The outlet and bypass conduits 134, 138, 140 are separate conduits connected directly to the unit 130.

In addition, the unit 100 may comprise monitoring elements, e.g. at least one flow sensor 150, e.g. a flow switch or some other appropriate sensor, switch or automation, for monitoring the flow of domestic water arriving through the exchanger 1 10. The sensor 150 detects e.g. that the shower faucet is turned on and the domestic water starts to flow through the exchanger, or that the shower faucet is turned off and the flow of domestic water comes to an end. The sensor 150 can also be positioned in the conduit 102 upstream of the ex- changer 1 10.

The unit 1 10 may further include a valve 152, e.g. a timed motor-operated or magnetic valve, for opening and closing the conduit 140. The valve 152 is adapted to be in an open condition and to open when the sensor 150 does not detect a flow of domestic water and to close and to be in a closed condition when a flow is detected.

The unit 1 10 may additionally include a control unit (electronics, automation) 154, which is adapted to control operation of the pump 120 and the valve 152 in response to observations arriving from the sensor 150, and a power source 156 for supplying power e.g. to the pump 120, the valve 152, and the unit 154. When there is no flow of domestic water in the conduit 104, i.e. the shower faucet is closed, the valve 152 is open. When the sensor 150 detects the presence of a flow in the conduit 104 as the shower faucet is turned on, the unit 154 receives a message thereof from the sensor 150 and thereby activates the pump 120. The pump 120 starts to pump outgoing water by way of the unit 130 and the open valve 152 into the conduit 140 and thence along the conduit 106 away from the unit 100 for as long as the valve 152 remains open. Some of the outgoing water may also proceed into the exchanger 1 10 and thereby into the conduit 106 despite the valve 152 being open.

When the valve 152 is open, the outgoing water that flows through the filter 132 into the conduit 140 is used for a pre-purification of the filter 132 (the dirt adhered to the internal surface and mesh eyelets) as the latter is in attachment with the filter unit 130, thereby maintaining the filter 132 in working order. The unit 154 controls the valve 152 to close with some predetermined time delay, which can be e.g. 0-10 s, or as the flow of water attains some predetermined parameter value, whereby the flow by way of the conduit 140 stops and the outgoing water flows into the exchanger 1 10 to heat domestic water. When the sensor 150 detects that there is no flow in the conduit 104 as the shower faucet is turned off, the unit 154 receives a message thereof and opens the valve 152, whereby the outgoing water pumped by the pump 120 again begins to flow by way of the unit 130 and the opened valve 152 so as to remove dirt accumulated by the filter 132 (the internal surface and mesh eye- lets) into the conduit 140. Some of the outgoing water may again proceed into the exchanger 1 10 as well.

After some predetermined time delay, which can be e.g. 0-10 s, or as the flow of water attains some predetermined parameter value, the pump 120 is turned off by the unit 154, thereby stopping a post-purification of the filter 132 through the use of outgoing water discharging by way of the conduit 140.

By virtue of a regular pre- and/or post-purification of the filter 132, the exchanger 1 10 has an efficiency of about 60% (especially with a plate heat exchanger), a prolonged service life and an increased maintenance interval, all of which bring down costs. Likewise, a blockage of the filter 132 is prevented more effectively and the maintenance interval increases, the costs being also reduced thereby.

In fig. 1 c is shown a protective enclosure 158 for the unit 100. The exchanger 1 10, the unit 130, the sensor 150, the valve 152, and the unit 154 - possibly also the power source 156 contrary to the figure - are installed in the protective enclosure 158, which in fig. 1 b misses a cover. The enclosure 158 comprises fittings (connections) for connecting the unit to a conduit for incoming domestic water, to a conduit for heated domestic water, to an outgoing water conduit, and to a conduit for cooled outgoing water.

The unit 100 may also comprise more than one exchanger 1 10. The unit 100 may also comprise identification elements for identifying a blockage of the filter 132 and notification elements, e.g. a signal light, for indicating to the user that the filter 132 is clogged and/or needs to be replaced, whereby he or she would know to replace the filter 132. The identification elements may comprise e.g. flow and/or temperature sensors e.g. in conduits 128, 134 and/or in a conduit 138 (valve 152), which monitor the flow and/or the temperature and communicate with the control unit 154 and/or another control unit present for the purpose. By virtue of a simple configuration of the unit 100, its manufacture and retrofitting is easy and economically sensible.

Figs. 2a-2e show various embodiments for a filter unit 230, which is used for the purification of water and which can be used e.g. in the unit 100.

The unit 230 comprises a filter 232 for the purification of water, a housing 260 for protecting the filter 232, and coupling elements 228, 234, 262 for connecting the unit 230 to water inlet and outlet conduits, e.g. for outgoing water.

In addition, the unit 230 comprises bypass elements 238, which make it possible to discharge from the unit 230 at least some of the water flowing through the filter 232 and to clean an internal surface of the filter 232 by means of wa- ter flowing through the filter 232 as the latter is in attachment with the housing 260. The bypass elements 268 may take the form of a bypass port 268 or a bypass conduit (fitting, adapter) 268.

The unit 230 may further comprise a maintenance opening 272 by way of which it is possible to remove the filter 232 from the housing 260, and closure elements 274, 276 for closing the maintenance opening 272. The closure elements 274, 276 may take the form of a cap 274 or a plug 276.

The unit 230 may additionally comprise guide elements 280, 282 for directing the filter in such a way that the filter 232 attaches to the housing 260. The guide elements 280, 282 may take the form of a jig 280 and/or a spring 282. In fig. 2a, the coupling elements 234, 262 of the unit 230, manufactured e.g. by machining from steel and/or aluminum and/or plastics, comprise an inlet port plug 262 which enables an attachment of the filter 232 to the housing 260 and a flow of water into the unit 230, an outlet port 234 which enables a flow of water out of the unit 230, and a bypass port 238 eccentric with respect to the out- let port 234.

Connecting the unit of fig. 2a to the inlet, outlet and bypass ports requires e.g. pipe fittings. In figs. 2b and 2c, in the unit 230 manufactured from plastics e.g. by injection molding - as also in figs. 2d and 2e - the coupling elements 228, 234 comprise an inlet conduit (fitting) 228 which enables a flow of water into the unit 230, an outlet conduit (fitting) 234 which enables a flow of water away, and a bypass conduit (fitting) 238 eccentric with respect to the outlet conduit 234. By virtue of the eccentricity, the unit 230 is improved in terms of its operation as it enables a higher flow rate in the unit 230.

As opposed to the unit 230 of fig. 2a, the units of figs. 2b-2d enable a simpler connection to the inlet, outlet and bypass ports by already including the fittings 228, 234, 238.

Described above are just a few embodiments of the invention. The principle according to the invention can naturally be varied within the scope of protection defined by the claims, regarding for example implementation details as well as fields of use.