Patent Description:
In the related art, a heat recovery system has been known in which in a compressor that compresses gas such as air, heat exchange is performed between a high-temperature fluid after compression and cooling water of a lower temperature therethan, to recover heat from the high-temperature fluid and to effectively use the heated cooling water. For example, Patent Document <NUM> discloses this type of technique in the related art.

In Patent Document <NUM>, a heat recovery heat exchanger is provided in an air path from a compressor to an air cooler, and allows heat exchange between compressed air and water to produce hot water. An air path from the compressor to the heat recovery heat exchanger and an air path from the heat recovery heat exchanger to the air cooler are connected to each other by a bypass path. In addiiton, in Patent Document <NUM>, an exhaust heat recovery hot water supply system for heating and supplying hot water using exhaust heat from a generator is shown. Herein, the respective system specifically comprises a heat exchanger connecting a hot water storage tank to exhaust heat line so as to efficiently regulate the heat of the exhaust heat line. In addition, also a supplementary cold water line is implemented to said heat exchanger, resulting in the effect that the exhaust heat line can be still regulated even in case the heat of the hot water storage tank reaches the same heat as the exhaust heat line. Moreover, in Patent Document <NUM>, a fuel cell system is disclosed to include a fuel cell supplied with fuel gas and reforming water to generate electric power, a first and a second heat exchanger path both for circulating a refrigerant between a refrigerant tank and an exhaust heat exchanger and a first and a second circulation path to equally circulating the refrigerant between the refrigerant tank and a tap water heat exchanger.

The compressed air from the compressor can be switched between flowing to the heat recovery heat exchanger and flowing to the bypass path. When the compressed air passes through the bypass path, the compressed air passes through the air cooler and during that time, is cooled by cooling water introduced from a cooling water path. The cooling water that is increased in temperature by heat taken from the compressed air is cooled by a cooling tower, and circulates through the cooling water path again.

When the compressed air passes through the air path, the compressed air passes through the heat recovery heat exchanger and during that time, heat of the compressed air heats water introduced from a water supply path, to produce hot water.

In Patent Document <NUM>, the cooling water path and the water supply path are separated from each other, and heat exchange between these water paths is not intended. It is only described that the cooling water after passing through the air cooler is increased in temperature and is cooled by the cooling tower to flow to the air cooler through the cooling water path again, but no attempt has been made to recover heat from hot water after passing through the air cooler.

On the other hand, the water from a water supply source passes through the heat recovery heat exchanger via the water supply path to become hot water during that time, but it is assumed that the temperature of the water before passing through the heat recovery heat exchanger is lower than the temperature of the cooling water after passing through the air cooler.

When the temperature of the water before passing through the heat recovery heat exchanger is lower than the temperature of the cooling water after passing through the air cooler, a low-temperature side can be preheated by transferring heat from a high-temperature side to the low-temperature side via any form of heat exchanger, but no such reference is made in Patent Document <NUM>.

As described above, in Patent Document <NUM>, it is not considered that liquid such as water can be preheated and then reheated by the heat recovery heat exchanger to supply the liquid of a higher temperature.

An object of the present invention is to allow the supply of supply water of a higher temperature by preheating the supply water and then by reheating the supply water with a heat recovery heat exchanger.

According to one aspect of the present invention, there is provided a heat recovery device connected to at least one compressor, the device including: an auxiliary cooling heat exchanger that performs auxiliary cooling; a heat recovery exchanger that heats supply water; a preheating heat exchanger that preheats and supplies the supply water to the heat recovery exchanger; a supply water path that supplies the supply water to the heat recovery exchanger; and a preheating bypass path which branches from the supply water path to supply the supply water to the preheating heat exchanger, and through which the supply water preheated by the preheating heat exchanger returns to the supply water path. The preheating heat exchanger allows heat exchange between cooling water on an outlet side of the auxiliary cooling heat exchanger and the supply water that has passed through the preheating bypass path.

According to one aspect of the present invention, there is provided a heat recovery device connected to at least one compressor, the device including: an auxiliary cooling heat exchanger that performs auxiliary cooling; a heat recovery exchanger that heats supply water; a preheating heat exchanger that preheats and supplies the supply water to the heat recovery exchanger; a supply water path that supplies the supply water to the heat recovery exchanger; and a preheating bypass path which branches from the supply water path to supply the supply water to the preheating heat exchanger, and through which the supply water preheated by the preheating heat exchanger returns to the supply water path. The preheating heat exchanger allows heat exchange between cooling water supplied from an outside through a cooling water path and the supply water that has passed through the preheating bypass path.

According to one aspect of the present invention, the supply water can be preheated and then reheated by the heat recovery heat exchanger to supply the supply water of a higher temperature.

Hereinbelow, embodiments will be described with reference to the drawings. Incidentally, in the drawings, portions denoted by the same reference signs indicate the same or equivalent portions.

A configuration of a heat recovery system of a first embodiment will be described with reference to <FIG>.

<FIG> illustrates a system diagram of a heat recovery system. In addition, effects obtained by the first embodiment will be described with reference to <FIG>.

In addition, the first embodiment illustrates an example where the present invention is applied to a water-cooled oil-free screw compressor as a compressor unit.

An oil-free screw compressor illustrated in <FIG> is configured to suction and compress gas (air in the present embodiment) and to discharge the compressed gas.

In <FIG>, a compressor unit <NUM> includes a single-stage compressor <NUM> that suctions air through an air path <NUM>, compresses the air to a predetermined pressure, and discharges the compressed air, and a water-cooled aftercooler <NUM> that cools the discharged high-temperature compressed air. A discharge air temperature sensor <NUM> that measures a temperature of the discharged high-temperature compressed air is installed on the air path <NUM> downstream from the compressor <NUM>.

In addition, a water-cooled oil cooler <NUM> is provided that cools a lubricant for lubrication of the compressor <NUM> and a drive mechanism (not illustrated), and the lubricant is supplied and circulated to each part through a lubricant path <NUM> according to internal needs of the compressor unit <NUM>. The compressor <NUM> and the oil cooler <NUM> are normally cooled by cooling water passing through a first cooling water path <NUM> and an oil cooler cooling path <NUM> branching from the first cooling water path <NUM>, and the cooling water in the first cooling water path <NUM> is circulated by a pump (not illustrated) that is separately installed, and heat of the cooling water is discharged to the outside by a cooling tower or the like (not illustrated).

Generally, the pump and the cooling tower are shared with an existing facility that are separate from the compressor unit <NUM> and a heat recovery unit <NUM> to be described later, and unless otherwise required as required specifications by a user, the compressor unit <NUM> or the heat recovery unit <NUM> does not directly control operation of the pump or the cooling tower. Here, the heat recovery unit <NUM> forms a heat recovery device.

In the heat recovery system, the heat recovery unit <NUM> is installed side by side with the compressor unit <NUM>. The heat recovery unit <NUM> includes a heat recovery heat exchanger <NUM>, an auxiliary cooling heat exchanger <NUM>, a preheating heat exchanger <NUM>, a circulation pump <NUM>, a temperature regulation valve <NUM>, a control valve <NUM>, a heat recovery cooling water temperature sensor <NUM>, a cooling water outlet temperature sensor <NUM>, and a supply water temperature sensor <NUM>.

A suction side of the circulation pump <NUM> is connected to an outlet side on a high-temperature fluid side of the heat recovery heat exchanger <NUM>. In addition, a discharge side of the circulation pump <NUM> is connected to a cooling water inlet side of the aftercooler <NUM> in the compressor unit <NUM>, and a cooling water outlet side of the aftercooler <NUM> is connected to an inlet side on the high-temperature fluid side of the heat recovery heat exchanger <NUM>, so that a second cooling water path <NUM> is formed. A water supply valve <NUM> is disposed on the second cooling water path <NUM> on the discharge side of the circulation pump <NUM>. The water supply valve <NUM> operates in connection with the start of operation of the compressor unit <NUM>, and is normally open during operation of the compressor unit <NUM>.

A supply water path <NUM> is a path through which liquid such as relatively low-temperature water is supplied from the outside, and through which the liquid exchanges heat with high-temperature cooling water that is increased in temperature after cooling the high-temperature compressed air in the aftercooler <NUM> and that passes through the high-temperature fluid side of the heat recovery heat exchanger <NUM> on the second cooling water path <NUM>, to be heated and returns to an outside hot water demand destination.

The liquid that circulates through the supply water path <NUM> is not particularly limited in its use, and examples of the liquid include water and the like that can be widely used for, for example, boiler supply water preheating, hot water heating, showering, and the like.

The temperature regulation valve <NUM> is provided at an outlet on the high-temperature fluid side of the heat recovery heat exchanger <NUM>. The heat recovery cooling water temperature sensor <NUM> is provided on a downstream side of the temperature regulation valve <NUM>, and the temperature regulation valve <NUM> operates to decrease a valve opening degree as the temperature measured by the heat recovery cooling water temperature sensor <NUM> increases, and to be fully closed at a predetermined heat recovery cooling water control temperature THC.

An auxiliary cooling bypass path <NUM> branches from a location between the outlet of the heat recovery heat exchanger <NUM> and the temperature regulation valve <NUM> on the second cooling water path <NUM>, to merge with a location between the downstream side of the temperature regulation valve <NUM> on the second cooling water path <NUM> and the heat recovery cooling water temperature sensor <NUM> via a path on a high-temperature fluid side of the auxiliary cooling heat exchanger <NUM>.

The temperature regulation valve <NUM> automatically regulates the opening degree according to a heat recovery cooling water temperature TH2 measured by the heat recovery cooling water temperature sensor <NUM>, to allow a part of or a total amount of the cooling water (heat recovery cooling water) in the second cooling water path <NUM> to flow to the auxiliary cooling bypass path <NUM>.

Low-temperature cooling water cooled by the cooling tower is supplied to a path on a low-temperature fluid side of the auxiliary cooling heat exchanger <NUM> through a third cooling water path <NUM>, and heat is exchanged between the high-temperature cooling water that has passed through the auxiliary cooling bypass path <NUM> and the low-temperature cooling water that has passed through the third cooling water path <NUM>. Therefore, when the heat recovery cooling water temperature TH2 measured by the heat recovery cooling water temperature sensor <NUM> reaches the predetermined heat recovery cooling water control temperature THC, the temperature regulation valve <NUM> is fully closed, and a total amount of the cooling water on the second cooling water path <NUM> is additionally cooled by the auxiliary cooling heat exchanger <NUM> after passing through the heat recovery heat exchanger <NUM>, to return to the second cooling water path <NUM>. Accordingly, the cooling water that is sufficiently cooled is supplied to the aftercooler <NUM>, so that the compressed air temperature at an outlet of the aftercooler <NUM> is always suppressed to a certain temperature or less, which is an object.

An inlet of a path on a high-temperature fluid side of the preheating heat exchanger <NUM> is connected to a downstream side of an outlet of the path on the low-temperature fluid side of the auxiliary cooling heat exchanger <NUM> on the third cooling water path <NUM>, and the cooling water outlet temperature sensor <NUM> is installed between the auxiliary cooling heat exchanger <NUM> and the preheating heat exchanger <NUM>.

On the other hand, on the supply water path <NUM>, a preheating bypass path <NUM> branches at a location upstream from an inlet on a low-temperature fluid side of the heat recovery heat exchanger <NUM>, to merge again with a location downstream from the branch point and upstream from the inlet on the low-temperature fluid side of the heat recovery heat exchanger <NUM> via a path on a low-temperature fluid side of the preheating heat exchanger <NUM>. In addition, the control valve <NUM> is provided on an outlet side of the preheating heat exchanger <NUM> on the preheating bypass path <NUM>. The supply water temperature sensor <NUM> is provided on an upstream side of a branch point where the preheating bypass path <NUM> branches from the supply water path <NUM>.

When a cooling water outlet temperature TC2 measured by the cooling water outlet temperature sensor <NUM> is higher than a supply water supply temperature TU1 measured by the supply water temperature sensor <NUM>, the control valve <NUM> operates to be opened, so that the relatively low-temperature water in the supply water path <NUM> before entering the heat recovery heat exchanger <NUM> can be preheated and increased in temperature.

The opening and closing of the control valve <NUM> can be controlled based on the cooling water outlet temperature TC2 and the supply water supply temperature TU1 to prevent that conversely, when the cooling water outlet temperature TC2 is lower than the supply water supply temperature TU1, the supply water supply temperature TU1 is decreased and consequently, the temperature of the supply water after exiting from the heat recovery heat exchanger <NUM> is decreased.

In <FIG>, the supply water temperature at the outlet of the heat recovery heat exchanger <NUM> and the heat recovery cooling water temperature when the preheating of the water (supply water) in the supply water path <NUM> is not performed in the related art are compared with those when preheating is performed in the present invention. In this comparison, the type of the heat exchanger and the water flow rate are the same between the related art and the present invention.

When flow directions of a high-temperature fluid and a low-temperature fluid are defined as countercurrent flow directions in which the amount of exchanged heat can be increased, and the heat recovery cooling water that is the high-temperature fluid flows from an A end to a B end of the heat recovery heat exchanger <NUM>, the supply water that is the low-temperature fluid flows from the B end to the A end of the heat recovery heat exchanger <NUM>.

Regarding a temperature condition for the comparison, the temperature of the high-temperature fluid (heat recovery cooling water) at the A end of the heat recovery heat exchanger <NUM> is fixed to a condition of the related art and of the first embodiment, and the temperature of the low-temperature fluid (supply water) at the B end of the heat recovery heat exchanger <NUM> in the first embodiment is set to a temperature obtained by adding a preheating temperature amount of the supply water to a temperature in the related art. Incidentally, in the calculation of the heat exchanger, temperature differences between the high-temperature fluid and the low-temperature fluid on an A end side and on a B end side are set to be the same.

It can be seen that when the temperature of the low-temperature fluid (supply water) at the B end increases by the amount of preheating, the temperature of the low-temperature fluid (supply water) at the A end is higher than the temperature under the condition of the related art.

Accordingly, a facility at the hot water demand destination that uses the supply water can use hot water of a higher temperature compared to the case where preheating is not performed, and a wide range of applications where hot water can be used can be expected.

Incidentally, the first cooling water path <NUM> and the third cooling water path <NUM> do not necessarily need to form independent circuits. Even when a configuration is employed in which a cooling tower (not illustrated) that cools the cooling water is shared and the first cooling water path <NUM> and the third cooling water path branch from a common path from an outlet of the cooling tower to the heat recovery system of the present invention, the functions of the first embodiment are not affected.

In addition, the types of the heat exchangers are not limited to specific types, but regarding the preheating heat exchanger <NUM>, since a temperature difference between the cooling water that is a high-temperature fluid and the supply water that is a low-temperature fluid is not so large, in order to increase the amount of exchanged heat, a plate type heat exchanger is more preferably used that has a relatively small external dimensions of the heat exchanger and is capable of increasing a heat transfer area.

As described above, the heat recovery system of the first embodiment is a heat recovery system including: the compressor <NUM> that compresses suctioned gas to discharge the compressed gas; the aftercooler <NUM> that cools the compressed gas; the oil cooler <NUM> that cools a lubricant; the first cooling water path <NUM> that supplies cooling water to the compressor <NUM> and the oil cooler <NUM>; the second cooling water path <NUM> through which cooling water is circulated between the aftercooler <NUM> and the heat recovery heat exchanger <NUM> by the circulation pump <NUM>; the supply water path <NUM> that exchanges heat with the high-temperature cooling water in the second cooling water path <NUM> via the heat recovery heat exchanger <NUM>; the auxiliary cooling heat exchanger <NUM> that allows cooling water of the third cooling water path <NUM> to cool a temperature downstream from the outlet of the heat recovery heat exchanger <NUM> on the second cooling water path <NUM> to a temperature that does not interfere with operation of the compressor <NUM>; and the auxiliary cooling bypass path <NUM> that allows the bypass of the cooling water to the auxiliary cooling heat exchanger <NUM>.

The cooling water on an outlet side of the auxiliary cooling heat exchanger <NUM> on the third cooling water path <NUM> and the supply water that has passed through the preheating bypass path <NUM> branching from the location upstream from the inlet of the heat recovery heat exchanger <NUM> on the supply water path <NUM> exchange heat with each other via the preheating heat exchanger <NUM>.

Further, when the measured value TC2 of the temperature sensor <NUM> provided at an outlet of the auxiliary cooling heat exchanger <NUM> on the third cooling water path <NUM> is higher than the measured value TU1 of the supply water temperature sensor <NUM> provided on the upstream side of the branch point of the preheating bypass path <NUM>, the control valve <NUM> provided on the preheating bypass path <NUM> on the outlet side of the preheating heat exchanger <NUM> is opened.

According to the first embodiment, in the heat recovery system that recovers heat of compressed gas from the water-cooled gas compressor, the cooling water that is increased in temperature after cooling the heat recovery system and the relatively low-temperature supply water to be supplied for use as hot water exchange heat with each other via the heat exchanger to preheat the supply water, and then the supply water is reheated by the heat recovery heat exchanger of the heat recovery system, so that the supply water of a higher temperature can be supplied. Accordingly, a heat recovery rate of the heat recovery system can be improved by also recovering heat from a low-temperature heat source that normally only exhausts heat.

A configuration of a heat recovery system of a second embodiment will be described with reference to <FIG>.

<FIG> illustrates a system diagram of the heat recovery system. In <FIG>, portions denoted by the same reference signs as those in <FIG> indicate the same or equivalent portions, and a description of the same portions as those in the first embodiment will be omitted.

The second embodiment illustrates a case where the compressor unit <NUM> of the first embodiment is configured as a two-stage oil-free air compressor including a low-pressure stage compressor <NUM>, a high-pressure stage compressor <NUM>, and an intercooler <NUM> that cools compressed air discharged from the low-pressure stage compressor <NUM>. This configuration is suitable for a relatively large compressor unit that discharges a larger amount of compressed air than the single-stage compressor unit described in the first embodiment.

Regarding the compressor unit <NUM>, the first cooling water path <NUM> branches to the oil cooler cooling path <NUM>, and allows cooling water to flow to the compressor <NUM> and the compressor <NUM>.

The second cooling water path <NUM> allows cooling water discharged from the circulation pump <NUM>, to flow to the intercooler <NUM> and thereafter, to flow to the aftercooler <NUM>. The configuration is such that the cooling water receives heat from the compressed air in two stages of the intercooler <NUM> and the aftercooler <NUM> to be sent to the heat recovery heat exchanger <NUM>.

In the case of a method in which the cooling water of the second cooling water path <NUM> flows to the intercooler <NUM> and the aftercooler <NUM> in series to perform heat recovery, the temperature of hot water that is extracted can be more increased than in the water flowing method illustrated in the first embodiment, and the amount of recovered heat is increased. At this time, since the amount of heat increases that enters the high-temperature fluid side of the auxiliary cooling heat exchanger <NUM> via the auxiliary cooling bypass path <NUM>, consequently, the amount of heat received by the cooling water on the third cooling water path <NUM> also increases. For this reason, a larger flow rate of the cooling water of the supply water path <NUM> can be preheated via the preheating heat exchanger <NUM> than in the case of the first embodiment.

As a flowing sequence of the cooling water of the second cooling water path <NUM>, it is desirable that the cooling water flows to the intercooler <NUM> prior to flowing to the aftercooler <NUM>. As a characteristic of the two-stage air compressor, the higher the cooling capacity of the intercooler <NUM> is, the more the compressed air is cooled and the smaller the volume is. For this reason, a pressure loss that is generated until the cooling water flows into the high-pressure stage compressor <NUM> can be suppressed to a small value, and the power consumption of the high-pressure stage compressor <NUM> can be reduced.

Since the cooling water initially flows to the intercooler <NUM>, the compressed air in the low-pressure stage that passes through the intercooler <NUM> can be cooled by the low-temperature cooling water compared to when the cooling water initially flows to the aftercooler <NUM>. For this reason, a decrease in the cooling performance of the intercooler <NUM> can be prevented, and an influence on the overall performance of the compressor unit <NUM> can be suppressed to a minimum.

A configuration of a heat recovery system of a third embodiment will be described with reference to <FIG>.

<FIG> illustrates a system diagram of the heat recovery system. In <FIG>, portions denoted by the same reference signs as those in <FIG> and <FIG> indicate the same or equivalent portions, and a description of the same portions as those in the first and second embodiments will be omitted.

In the third embodiment, the third cooling water path <NUM> is configured to branch from the first cooling water path <NUM> at a location upstream from the heat recovery unit <NUM>. Namely, low-temperature cooling water is supplied to the first cooling water path <NUM> and the third cooling water path <NUM> from a common cooling tower installed outside.

The third cooling water path <NUM> merges with the first cooling water path <NUM> after cooling devices inside the compressor unit <NUM>, at a point downstream from the auxiliary cooling heat exchanger <NUM>. A bypass path <NUM> branches from the same merge point to merge with the first cooling water path at a point downstream from an outlet on the high-temperature fluid side of the preheating heat exchanger <NUM>.

A control valve <NUM> is installed on the bypass path <NUM>. In addition, a check valve <NUM> is provided at the outlet of the auxiliary cooling heat exchanger <NUM> on the third cooling water path <NUM> to prevent the high-temperature cooling water of the first cooling water path <NUM> from flowing back to a third cooling water path <NUM> side.

The cooling water outlet temperature sensor <NUM> is installed between a merge point between the first cooling water path and the third cooling water path, and an inlet of the preheating heat exchanger <NUM>, instead of being installed at the position described in the first and second embodiments.

when the cooling water outlet temperature TC2 is higher than the supply water supply temperature TU1, the control valve <NUM> is opened and the control valve <NUM> is closed to preheat supply water. When the cooling water outlet temperature TC2 is lower than the supply water supply temperature TU1, the control valve <NUM> is closed and the control valve <NUM> is opened not to preheat the supply water.

In addition, when the heat recovery cooling water temperature TH2 measured by the heat recovery cooling water temperature sensor <NUM> is a heat recovery cooling water upper limit temperature THL or more, control is performed such that the control valve <NUM> is closed and the control valve <NUM> is opened not to preheat the supply water.

In the third embodiment, since the cooling water of the first cooling water path cools the oil cooler <NUM>, the low-pressure stage compressor <NUM>, and the high-pressure stage compressor <NUM>, a larger amount of heat can be recovered than the case of the single-stage compressor unit <NUM> illustrated in the first embodiment, and an increase in temperature by preheating can be further increased or a larger flow rate of the supply water can be preheated in combination with the amount of heat that the cooling water of the third cooling water path receives from the auxiliary cooling heat exchanger <NUM>.

Further, in the first and second embodiments, the supply water can be preheated only while the temperature regulation valve <NUM> allows the bypass of the heat recovery cooling water to the auxiliary cooling heat exchanger <NUM>. According to the third embodiment, even while the temperature regulation valve <NUM> does not allow the bypass of the cooling water, the high-temperature cooling water of the first cooling water path <NUM> is allowed to flow to the preheating heat exchanger <NUM>, so that preheating can be more effectively performed.

On the other hand, when the temperature of the cooling water of the first cooling water path <NUM> after cooling the compressor unit <NUM> is abnormally high for any reason, the supply water is excessively preheated, and consequently, the heat recovery cooling water is insufficiently cooled by the heat recovery heat exchanger <NUM> and the auxiliary cooling heat exchanger <NUM>. As a result, when the temperature of the heat recovery cooling water supplied to the compressor unit <NUM> is higher than the heat recovery cooling water upper limit temperature THL, there is a possibility that the cooling performance of the intercooler <NUM> is decreased and a defect occurs in the compressor unit <NUM>.

In order to prevent this possibility, when the heat recovery cooling water temperature TH2 is the heat recovery cooling water upper limit temperature THL or more, control is performed such that the control valve <NUM> is closed and the control valve <NUM> is opened not to preheat the supply water. In order to prevent hunting of the valve or the like, in consideration of a margin, the heat recovery cooling water upper limit temperature THL is set to a temperature slightly higher than the heat recovery cooling water control temperature THC that is a temperature where the temperature regulation valve is fully closed.

In the first to third embodiments, the control valve <NUM> may be configured as a three-way vale capable of switching between water flowing and water stopping between one common direction and either of the remaining two directions among fluid paths in three directions, and when the control valve <NUM> is installed at a merge point between the supply water path <NUM> and the preheating bypass path <NUM> on the outlet side of the preheating heat exchanger <NUM> to preheat the supply water, the control valve <NUM> may be configured to be controlled such that a total amount of the supply water that flows through the supply water path <NUM> flows to the preheating heat exchanger <NUM> and the supply water is preheated and reheated by the heat recovery heat exchanger <NUM>. With this configuration, a total amount of the supply water can be preheated by the preheating heat exchanger <NUM>, and an improvement in heat recovery efficiency can be expected. On the other hand, when preheating is not performed, similarly, control is performed such that the control valve <NUM> is controlled to stop the flowing of the supply water to a preheating heat exchanger <NUM> side and to allow a total amount of the supply water to flow to the heat recovery heat exchanger <NUM>.

Incidentally, the present invention is not limited to the above-described embodiments, and includes various modification examples. For example, in the embodiments, the example has been described in which the present invention is applied to the oil-free screw compressor; however, the present invention is not limited thereto, can also be applied to oil-cooled screw compressors or water-injection type screw compressors in the same manner, and can be applied to any fluid machine such as scroll compressors, roots blowers, and turbochargers in the same manner.

In addition, in the above-described embodiments, an example of the screw compressor including a pair of male and female screw rotors in a rotor chamber has been described; however, the present invention can also be applied to a single screw compressor including one screw rotor in the same manner. In addition, in the first to third embodiments, the example has illustrated in which water is used as the cooling water that circulates through the first cooling water path and through the second cooling water path <NUM>; however, a case can be assumed in which a coolant liquid containing an antifreeze component such as alcohols, or oil is used, and the cooling water is not limited to only water. Further, a fluid that is supplied to the outside through the supply water path <NUM> after heat recovery is also not limited to water, and various fluids are assumed to be used as the fluid. The fluid is not limited to supply water, and a "supply liquid" may be considered as the fluid.

In addition, in the second and third embodiments, the intercooler <NUM> and the aftercooler <NUM> are connected to each other in series on the second cooling water path <NUM>, but may be connected to each other in parallel. The flowing sequence of the cooling water on the first cooling water path <NUM> is a typical sequence, but is not limited thereto, and a sequence may be employed in which the cooling water initially flows to the high-pressure stage compressor <NUM> and then flows to the low-pressure stage compressor <NUM>.

In the first to third embodiments, the preheating heat exchanger <NUM> is configured to be built in the heat recovery unit <NUM>; but even when the preheating heat exchanger <NUM> is configured to be separately installed outside the heat recovery unit <NUM>, the function is not affected.

In the first and second embodiments, the first cooling water path and the third cooling water path have been described as being independent of each other for convenience; but as in the third embodiment, even when the path is configured such that the outside cooling tower is shared and the third cooling water path branches from the first cooling water path outside the heat recovery system to merge again with each other, the functions of the present invention are not affected.

Claim 1:
A heat recovery device (<NUM>) connectable to at least one compressor (<NUM>), the device comprising:
an auxiliary cooling heat exchanger (<NUM>) that performs auxiliary cooling;
a heat recovery heat exchanger (<NUM>) that heats supply water;
a preheating heat exchanger (<NUM>) that preheats and supplies the supply water to the heat recovery heat exchanger (<NUM>);
a supply water path (<NUM>) that supplies the supply water to the heat recovery heat exchanger (<NUM>); and
a preheating bypass path (<NUM>) which branches from the supply water path (<NUM>) to supply the supply water to the preheating heat exchanger (<NUM>), and through which the supply water preheated by the preheating heat exchanger (<NUM>) returns to the supply water path (<NUM>),
wherein the preheating heat exchanger (<NUM>) allows heat exchange between cooling water on an outlet side of the auxiliary cooling heat exchanger (<NUM>) and the supply water that has passed through the preheating bypass path (<NUM>).