EP4261477A1

EP4261477A1 - Heat source unit

Info

Publication number: EP4261477A1
Application number: EP23162128.5A
Authority: EP
Inventors: Tooru Suga
Original assignee: Toshiba Carrier Corp
Current assignee: Toshiba Carrier Corp
Priority date: 2022-04-15
Filing date: 2023-03-15
Publication date: 2023-10-18
Also published as: JP2023157663A

Abstract

To accurately detect a condition of nonflowing usage fluid in a heat exchanger, a heat source unit includes a compressor configured to compress a refrigerant, a heater configured to heat the compressor, a first heat exchanger configured to exchange heat between the refrigerant and usage fluid, a first temperature sensor disposed on the first heat exchanger, a second temperature sensor disposed on the first heat exchanger in a position where heat amount to be received by heat radiation from the heater is different from the first temperature sensor, and a controller configured to prohibit start-up of the compressor based on difference between temperatures detected by the first temperature sensor and the second temperature sensor.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

Embodiments of the present invention relate to a heat source unit.

Description of the Related Art

In a known heat source unit of heat pump type, a compressor, an evaporator, an expansion valve, and a condenser are connected via refrigerant piping such that a refrigerant circulates through these components. The condenser constitutes a radiation section of the heat source unit, and the evaporator constituting a cooling section absorbs heat from the air or other fluid. The condenser exchanges heat between the refrigerant and fluid to be used (for example, water), and discharges the heat absorbed by the evaporator to the fluid to be used. The fluid to be used is hereinafter referred to as "usage fluid". The heated usage fluid, e.g., hot water, is supplied to an external device that is subject to heating. The condenser and the evaporator are both constituted as a heat exchanger in general. In another known heat source unit having both heating and cooling functions, the evaporator and the condenser are exchanged by inverting the refrigeration cycle to enable cooling of the usage fluid and supply of the cooled usage fluid to an external device.
In such a heat source unit, a pump is installed on the external device side, and this pump is driven to circulate the usage fluid (i.e., cause the usage fluid to flow) between the external device and the heat source unit. As the external device, there are various types of utilization form such as a hot water tank, or a heat exchanger for heat radiation or heat absorption that performs air conditioning of the room.
In a known technique, a pump interlock mechanism is installed in the heat source unit to prohibit the operation of the compressor under the condition where the pump configured to circulate the usage fluid on the external device side is stopped. This configuration prevents freezing of the evaporator and/or excessive load on the entirety of the heat source unit (Patent Document 1).
[Patent Document 1] JP H10-078266 A
However, even when the pump is stopped, the prohibition of the operation may be unintentionally removed due to occurrence of a short circuit in the terminals of the pump interlock mechanism for some reason. In addition, even when the pump is energized, there may be a case where the pump is stopped due to a failure of the pump itself. Further, in the piping for circulating the usage fluid between the heat source unit and the external device, scale gradually accumulates inside during long-term use, and consequently, the piping is clogged in some cases. In such cases, the usage fluid does not flow even if the pump is operated, and even if the terminal of the pump interlock mechanism receives a signal indicating that the pump is in operation, a situation of nonflowing usage fluid (i.e., a situation where the usage fluid is not actually flowing) occurs. Such a situation can be avoided by directly detecting the flow rate of the usage fluid flowing through the piping between the heat source unit and the external device. In this case, however, it is necessary to add special parts such as a flow rate sensor, which increases the cost and the number of parts.

SUMMARY OF THE INVENTION

In view of the above-described circumstances, an object of the present invention is to provide a heat source unit that can accurately detect a condition of nonflowing usage fluid without using a so-called pump interlock mechanism while suppressing increase in number of parts.
In one aspect of the present invention, a heat source unit includes a compressor configured to compress a refrigerant, a heater configured to heat the compressor, a first heat exchanger configured to exchange heat between the refrigerant and usage fluid, a first temperature sensor disposed on the first heat exchanger, a second temperature sensor disposed on the first heat exchanger in a position where heat amount to be received by heat radiation from the heater is different from the first temperature sensor, and a controller configured to prohibit start-up of the compressor based on difference between temperature detected by the first temperature sensor and temperature detected by the second temperature sensor.
The heat source unit may include a compressor configured to compress a refrigerant, a heater disposed on an outer periphery of the compressor in such a manner that the heater can heat the compressor, a first heat exchanger configured to exchange heat between the refrigerant and usage fluid, a housing that houses the compressor and the first heat exchanger, a first temperature sensor disposed at an inlet of the usage fluid with respect to the first heat exchanger, the second temperature sensor disposed at an outlet of the usage fluid with respect to the first heat exchanger, the outlet being different from the inlet in terms of heat amount to be received by heat radiation from the heater, the controller configured to acquire respective detection signals output from the first temperature sensor and the second temperature sensor, and prohibit start-up of the compressor when temperature difference corresponding to difference between a detection signal of the first temperature sensor and a detection signal of the second temperature sensor is equal to or larger than a predetermined value during operation of the heater.
The heater may include a belt heater wrapped around the compressor.
The inlet and the outlet of the usage fluid may be different in heat amount to be received from the heater by being different in position in a height direction or distance from the heater.
The heat amount to be received by heat radiation from the heater may be larger at the outlet of the usage fluid than at the inlet.
The outlet of the usage fluid may be disposed higher than the inlet or closer to the heater than the inlet.
The outlet of the usage fluid may be disposed at a height closer to the top portion of the belt heater than to the bottom portion, while the inlet may be disposed at a height closer to the bottom portion of the belt heater than to the top portion.
The outlet of the usage fluid may be disposed at or above a height of the top portion of the belt heater, while the inlet may be disposed at or near a height of the bottom portion of the belt heater.
The heat amount to be received by heat radiation from the heater may be larger at the inlet of the usage fluid than at the outlet.
The inlet of the usage fluid may be disposed higher than the outlet or closer to the heater than the outlet.
The housing may have a partition plate that partitions interior of the housing, and the compressor and the first heat exchanger may be housed in the same space partitioned by the partition plate.
The usage fluid may be water.
The heat source unit may further include an expansion valve, a second heat exchanger, and refrigerant piping disposed in such a manner that the refrigerant can be circulated between the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger. The first heat exchanger may be configured to cool the usage fluid by heat exchange with the refrigerant, and the second heat exchanger may be configured to discharge heat from the refrigerant after the usage fluid is cooled by the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

Fig. 1 is a schematic diagram illustrating an overall configuration of a heat source unit according to one embodiment of the present invention;
Fig. 2 is a schematic diagram illustrating electrical connection relationship between a compressor and its peripheral components in the heat source unit;
Fig. 3 is a plan view illustrating positional relationship of internal components when a housing of the heat source unit is viewed from above;
Fig. 4 is an elevational view illustrating the positional relationship of the internal components when the housing of the heat source unit is viewed from the side;
Fig. 5 is a flowchart illustrating contents of a basic control routine of the heat source unit;
Fig. 6 is a flowchart illustrating contents of compressor start-up control included in the basic control routine;
Fig. 7 is a graph illustrating respective changes in inlet liquid temperature Twi, outlet liquid temperature Two, and temperature difference ΔTw in the case of de-energizing the heater under the condition where there is no flow in usage fluid;
Fig. 8 is a graph illustrating respective changes in the inlet liquid temperature Twi, the outlet liquid temperature Two, and the temperature difference ΔTw when the condition of nonflowing usage fluid is maintained after starting to energize the heater; and
Fig. 9 is a graph illustrating respective changes in the inlet liquid temperature Twi, the outlet liquid temperature Two, the temperature difference ΔTw, and flow rate Rcw of the usage fluid when water flow is started from the condition where there is no flow in usage fluid.

DETAILED DESCRIPTION

Hereinbelow, embodiments of the present invention will be described by referring to the accompanying drawings.
The configuration of a heat source unit U shown in Fig. 1 will be described by referring to Fig. 2 to Fig. 4 as appropriate.
In the present embodiment, the heat source unit U constitutes a refrigeration cycle apparatus of heat pump type and can cool or heat usage fluid to be circulated between the heat source unit U itself and an external device (not shown) such as a cooling/heating apparatus or a hot water storage device. Although water is generally used as the usage fluid, brine may also be used as the usage fluid for antifreeze purposes. The refrigerant is, for example, an R410A refrigerant, an R32 refrigerant, or a CO₂ refrigerant containing carbon dioxide (CO₂). In the present embodiment, water is used as the usage fluid. In Fig. 1, the solid arrows indicate the flow of the refrigerant during cold water generation for supplying cold water (i.e., the usage fluid after being cooled) to the external device, and the dotted arrows indicate the flow of the refrigerant during hot water generation for supplying warm water or hot water (i.e., the usage fluid after being heated) to the external device.
The heat source unit U includes: a compressor 1; a first heat exchanger 2; a second heat exchanger 3; a four-way valve 4; and an expansion valve 5, as its main components. The heat source unit U further includes refrigerant piping 6 that fluidly connects these components and circulates the refrigerant between these components. As shown in Fig. 3 and Fig. 4, the compressor 1, the first heat exchanger 2, the second heat exchanger 3, the four-way valve 4, the expansion valve 5, and the refrigerant piping 6 are housed inside a housing C. The housing C is installed outdoors. The housing C is configured as a high-strength metal casing made of, for example, a box-shaped sheet metal. On part of a side surface of the housing C, an opening for ventilation to the second heat exchanger 3 is formed.
The compressor 1 is an internally high-pressure hermetic rotary compressor that compresses and pressurizes the refrigerant and then discharges the refrigerant, for example. The compressor 1 has a sealed iron pressure-resistant vessel as its outer body, and a rotary compression mechanism is housed inside the pressure-resistant vessel. In the lower portion of this sealed pressure-resistant vessel, lubricating oil for lubricating the compression mechanism is stored. The compressor 1 can change its operating frequency by known inverter control. This operating frequency does not necessarily have to be changeable, and the compressor 1 may be configured to operate at a constant speed by using a commercial frequency.
On the outer periphery of the compressor 1, a heater 7 is disposed so as to be able to heat the compressor 1, more specifically, transfer heat to the inside of the compressor 1. For the heater 7, a belt heater or a cord heater can be adopted, for example. Wrapping the belt heater 7 around the compressor 1 and disposing an appropriate heat insulating material around the belt heater 7 enables the compressor 1 to be heated and maintain its temperature. The heat generated by the heater 7 is transmitted to the inside of the compressor 1 and is stored inside so as to: heat the lubricating oil for lubricating the compression mechanism inside the compressor 1; and maintain proper viscosity of the lubricating oil even during the shutdown period of the compressor 1.
The first heat exchanger 2 exchanges heat between the refrigerant and the usage fluid. The first heat exchanger 2 is, for example, a coil-type water-refrigerant heat exchanger in which a pipe 2a for circulating the refrigerant and a pipe 2b for circulating the usage fluid (hereinafter referred to as "the water flow pipe 2b") are formed in coil shapes and are joined or welded to each other. The first heat exchanger 2 is not limited to the coil type but may be a plate type heat exchanger in which a plurality of thin plates are stacked and the refrigerant and the usage fluid flow alternately in the gaps between adjacent plates. In Fig. 1, the piping structure is simplified for facilitating the understanding, and the pipe 2a for circulating the refrigerant and the water flow pipe 2b for circulating the usage fluid inside the first heat exchanger 2 are respectively indicated by thick dotted lines.
As shown in Fig. 3 and Fig. 4, on the back-surface side of the housing C that houses the components of the heat source unit U, piping joints j1 and j2 are respectively provided at the inlet and outlet of the usage fluid. The usage fluid is introduced into the heat source unit U from the inlet pipe p1 extending from the external device via the inlet piping joint j1, and flows into the water flow pipe 2b inside the first heat exchanger 2. The usage fluid having been subjected to heat exchange with the refrigerant flows out of the water flow pipe 2b and is discharged from the first heat exchanger 2, i.e., from the heat source unit U via the outlet piping joint j2. The usage fluid having flowed out of the heat source unit U is supplied to the external device via the outlet pipe p2. In Fig. 1, the flow of the usage fluid is indicated by thick arrows.
The second heat exchanger 3 exchanges heat between the refrigerant and the air, for example, the outside air. The second heat exchanger 3 is, for example, a fin-and-tube air/refrigerant heat exchanger, and includes a tube 31 made of a copper pipe and a plurality of fins 32 made of thin aluminum plates (Fig. 3). The second heat exchanger 3 further includes a fan F and a motor M as its drive source. The second heat exchanger 3 forcibly forms a flow of the air (outside air) along the surface of the fins 32 by using the fan F and thereby facilitates heat transfer between the air and the refrigerant flowing inside the tube 31.
As shown in Fig. 3, the interior of the housing C is partitioned into right and left to form a fan chamber A and a machine chamber B by a partition plate 9 extending in the vertical direction. In the fan chamber A, the second heat exchanger 3 and the fan F are housed. The side surface of the housing C facing the second heat exchanger 3 is provided with an opening for ventilation. The machine chamber B houses refrigeration cycle components other than the fan F and the second heat exchanger 3, specifically, the compressor 1, the first heat exchanger 2, the four-way valve 4, and the like. The partition plate 9 is formed of, for example, a sheet metal, and is attached to the housing C in such a manner that liquid such as rainwater having entered the fan chamber A through the opening does not enter the machine chamber B. Further, the outer body including the partition plate 9 and a top plate 10 (Fig. 4) of the housing C prevents direct intrusion of liquid such as rainwater into the machine chamber B from the outside. The compressor 1 and the first heat exchanger 2 are disposed to be close to each other inside the machine chamber B.
The four-way valve 4 switches the flow path of the refrigerant discharged from the compressor 1 between a cold water generation span and a hot water generation span. During the cold water generation, the four-way valve 4 sets the flow path of the refrigerant to the direction from the four-way valve 4 to the second heat exchanger 3, and consequently, the refrigerant having flowed out of the four-way valve 4 passes through the second heat exchanger 3 and then flows into the first heat exchanger 2. During the hot water generation, the flow path of the refrigerant is switched into the direction from the four-way valve 4 to the first heat exchanger 2, and consequently, the refrigerant having flowed out of the four-way valve 4 passes through the first heat exchanger 2 and then flows into the second heat exchanger 3.
The expansion valve 5 is a valve configured to adjust the pressure of the refrigerant having flowed out of the condenser (for example, the second heat exchanger 3 that functions as a condenser during the cold water generation) by action of an orifice. The expansion valve 5 uses flow resistance for creating pressure drop and thereby regulates the pressure of the refrigerant that flows toward the evaporator (for example, the first heat exchanger 2 that functions as an evaporator during the cold water generation). As a component applicable to the expansion valve 5, for example, an electronic expansion valve to be driven by a stepping motor can be used.
The refrigerant piping 6 connects the compressor 1, the first heat exchanger 2, the second heat exchanger 3, the four-way valve 4, and the expansion valve 5 such that the refrigerant can circulate through these components 1 to 5. In the present embodiment, the refrigerant piping 6 is roughly divided into: a first refrigerant pipe 6a connected to the compressor 1 and the four-way valve 4; a second refrigerant pipe 6b connected to the four-way valve 4 and the second heat exchanger 3; a third refrigerant pipe 6c connected to the second heat exchanger 3 and the expansion valve 5; a fourth refrigerant pipe 6d connected to the expansion valve 5 and the first heat exchanger 2; a fifth refrigerant pipe 6e connected to the first heat exchanger 2 and the four-way valve 4; and a sixth refrigerant pipe 6f connected to the four-way valve 4 and the compressor 1.
During the cold water generation, the four-way valve 4 connects an inflow port 4a to a first inflow/outflow port 4b and also connects a second inflow/outflow port 4c to an outflow port 4d. Switching of the flow path by the four-way valve 4 is performed by control of a pilot valve (not shown). During the cold water generation, the second heat exchanger 3 disposed on the upstream side with respect to the refrigerant flow operates as a condenser or a radiator, and the first heat exchanger 2 disposed on the downstream side operates as an evaporator or a heat absorber. The refrigerant discharged from the compressor 1 flows toward the second heat exchanger 3 via the four-way valve 4, then receives the action of the expansion valve 5, then passes through the first heat exchanger 2, and then returns to the compressor 1 via the four-way valve 4.
During the hot water generation, controlling of the pilot valve causes the four-way valve 4 to: switch the connection destination of the inflow port 4a to the second inflow/outflow port 4c; and switch the connection destination of the outflow port 4d to the first inflow/outflow port 4b. During the hot water generation, the first heat exchanger 2 disposed on the upstream side with respect to the refrigerant flow operates as a condenser or a radiator, and the second heat exchanger 3 disposed on the downstream side operates as an evaporator or a heat absorber. The refrigerant discharged from the compressor 1 flows toward the first heat exchanger 2 via the four-way valve 4, then receives the action of expansion valve 5, then passes through second heat exchanger 3, and then returns to the compressor 1 via the four-way valve 4.
In addition to the above-described components, the heat source unit U includes: a controller 101; an inlet temperature sensor 111; an outlet temperature sensor 112, an operation switch 113; and a display 114, as control-system components. In the present embodiment, the heat source unit U further includes a relay 115 for energizing the heater described below. The controller 101 has a control circuit including an inverter circuit and/or a microcomputer. The controller 101 may be disposed in the machine chamber B or may be disposed in the upper portion inside the housing C across the machine chamber B and the fan chamber A by being supported by the partition plate 9, for example.
As shown in Fig. 1 and Fig. 4, the inlet temperature sensor 111 detects temperature Twi of the usage fluid flowing into the first heat exchanger 2, specifically, the water flow pipe 2b of the first heat exchanger 2. The inlet temperature sensor 111 is, for example, a thermistor and is disposed at the inlet of the usage fluid with respect to the first heat exchanger 2. In the present embodiment, the inlet temperature sensor 111 is disposed on a first relay pipe that connects the first heat exchanger 2 to the inlet piping joint j1, more specifically, on the portion of the first relay pipe close to the first heat exchanger 2.
The outlet temperature sensor 112 detects temperature Two of the usage fluid flowing out of the first heat exchanger 2, specifically, the water flow pipe 2b of the first heat exchanger 2. The outlet temperature sensor 112 can be configured as a thermistor similarly to the inlet temperature sensor 111, and is disposed at the outlet of the usage fluid with respect to the first heat exchanger 2. In the present embodiment, the outlet temperature sensor 112 is disposed on a second relay pipe that connects the first heat exchanger 2 to the outlet piping joint j2, more specifically, on the portion of the second relay pipe close to the first heat exchanger 2 (Fig. 3). The inlet temperature sensor 111 and the outlet temperature sensor 112 are disposed in the machine chamber B together with the first heat exchanger 2.
The operation switch 113 is a switch that instructs the heat source unit U to operate and stop. The operation switch 113 is, for example, a push button switch to be operated by a user.
The display 114 displays the operation state of the heat source unit U, is arranged outside the housing C, and allows a user to check the displayed contents and perform operations. In the present embodiment, the display 114 is communicably connected to the controller 101. Further, the display 114 has an operation panel in addition to a screen, and the operation switch 113 is incorporated in the operation panel and formed integrally with the display 114.
The controller 101 receives respective detection signals outputted from the inlet temperature sensor 111 and the outlet temperature sensor 112, and also receives various operation signals from the operation switch 113 and the display 114 so as to control the operation of the compressor 1 and the belt heater 7.
Referring to the circuit diagram of Fig. 2, the compressor 1 is connected to a commercial AC power supply 11 via a rectifier 12, a capacitor 13, and an inverter 14, and is configured so as to be able to change its operating frequency (i.e., number of rotations) by the inverter 14. The heat source unit U is always in the state of being supplied with electric power from the commercial AC power supply 11 unless an upstream circuit breaker (not shown) trips. Thus, the controller 101 and the display 114 receive operating power from the power supply 11 and can always continue the control operation regardless of whether the operation switch 113 is turned on or turned off.
The belt heater 7 is connected in parallel with the rectifier 12 to the power supply 11, and the circuit that connects the belt heater 7 to the power supply 11 is provided with the relay 115. The relay 115 operates in accordance with a command signal from the controller 101. In detail, in response to an ON command from the controller 101, the relay 115 closes the circuit so as to energize the belt heater 7 and cause the belt heater 7 to operate. In response to an OFF command from the controller 101, the relay 115 opens the circuit so as to shut down energization of the belt heater 7 and stop the heating operation of the belt heater 7. The ON/OFF control of the belt heater 7 is described below in detail by referring to the flowchart of Fig. 5.
Referring to Fig. 3 and Fig. 4, the inlet temperature sensor 111 and the outlet temperature sensor 112 are disposed at different heights. In detail, the outlet temperature sensor 112 is in a higher position than the inlet temperature sensor 111.
More specifically, the compressor 1 is disposed on the back-surface side of the first heat exchanger 2. On the front side of the first heat exchanger 2, the inlet temperature sensor 111 is disposed at the inlet adjacent to the introduction-side opening of the water flow pipe 2b and is disposed at a height near the bottommost portion of the installation region of the belt heater 7 on the outer periphery of the compressor 1. On the front side of the first heat exchanger 2, the outlet temperature sensor 112 is disposed at the outlet adjacent to the discharge-side opening of the water flow pipe 2b and is disposed at a height higher than the topmost portion of the installation region of the belt heater 7. The installation region of the belt heater 7 refers to the range of the outer periphery of the compressor 1 surrounded by the belt heater 7, and Fig. 4 schematically indicates this installation region by a two-dot chain line.
In the present embodiment, inside the housing C, the partition plate 9 separates the fan chamber A, where the second heat exchanger 3 and the fan F are disposed, and the machine chamber B, where the compressor 1 and the first heat exchanger 2 are disposed, from each other. The machine chamber B is airtight to some extent. Accordingly, during the operation of the compressor 1, part of the air flow generated by the fan F may be caused to flow into the machine chamber B in order to cool the inverter 14. However, during the shutdown period of the compressor 1 (i.e., while the refrigeration cycle is stopped), the fan F also stops and thus, there is almost no circulation of the outside air into the machine chamber B.
Consequently, between the inlet temperature sensor 111 and the outlet temperature sensor 112, i.e., between the inlet of the first heat exchanger 2 as the installation position of the inlet temperature sensor 111 and the outlet of the first heat exchanger 2 as the installation position of the outlet temperature sensor 112, difference occurs in heat amount to be received by convective heat transfer in which the belt heater 7 functions as the heat source. In detail, the heat amount to be received by the outlet temperature sensor 112 becomes larger than the heat amount to be received by the inlet temperature sensor 111. In Fig. 4, the height difference between the inlet temperature sensor 111 and the outlet temperature sensor 112 is indicated by the reference sign Δh.
Returning to Fig. 1, the controller 101 receives various signals outputted by the inlet temperature sensor 111, the outlet temperature sensor 112, and the operation switch 113, and outputs command signals to the compressor 1, the belt heater 7, the display 114, and the relay 115.
In the present embodiment, the controller 101 avoids the operation of the heat source unit U, specifically prohibits the start-up of the compressor 1, under the condition where there is no flow of the usage fluid especially due to stoppage of the pump installed in the external device, for example. The method will be described in reference to the flowcharts shown in Fig. 5 and Fig. 6.
The controller 101 starts the control based on the routines shown in Fig. 5 and Fig. 6 in response to an operation of turning on the operation switch 113 by the user, and then repeatedly executes the routines until the user turns off the operation switch 113.
In the step S101, it is determined whether the operation switch 113 of the heat source unit U is in the ON state or not, i.e., whether the operation switch 113 is turned on or not. If the operation switch 113 is in the ON state, the processing proceeds to the step S102. If the operation switch 113 is not in the ON state, i.e., if the operation switch 113 is in the OFF state, the processing proceeds to the step S107 in which the controller 101 stops the compressor 1 regardless of whether the compressor 1 is in operation or stopped.
In the next step S102, the belt heater 7 is activated and then this routine is repeated. Since the belt heater 7 continues to be energized even while the heat source unit U is stopped in this manner, the compressor 1 is always maintained at an appropriate temperature. As a result, when the operation switch 113 is turned on, the compressor 1 can be activated immediately and the heat source unit U can start operating.
In the step S102, the controller 101 reads in the temperature Twi of the usage fluid detected by the inlet temperature sensor 111 (hereinafter referred to as "the inlet liquid temperature Twi") and the temperature Two of the usage fluid detected by the outlet temperature sensor 112 (hereinafter referred to as "the outlet liquid temperature Two"), and then the processing proceeds to the step S103.
In the step S103, a drive frequency Fcmp of the compressor 1 is set. The setting of the drive frequency Fcmp is based on: difference between the inlet liquid temperature Twi and its target temperature or between the outlet liquid temperature Two and its target temperature; and amount of temporal change in this difference, for example.
In the step S104, it is determined whether the drive frequency Fcmp having been set in the S103 is 0 or not, i.e., whether the condition(s) for stopping the compressor 1 is/are satisfied or not. For example, if the inlet liquid temperature Twi is higher than the target temperature, the drive frequency Fcmp becomes 0 and the compressor 1 is stopped. If the drive frequency Fcmp is 0 (YES in the step S104), the processing proceeds to the step S105. If the drive frequency Fcmp is not 0 (NO in the step S104), the processing proceeds to the step S106.
In the step S105, it is determined whether the drive frequency Fcmp having been set in the routine right before the currently running routine (hereinafter, shortly referred to as "the previous routine") is 0 or not. In other words, the controller 101 determines whether the compressor 1 is stopped or not by determining whether the drive frequency Fcmp is also 0 or not in the currently running routine following the previous routine. If the drive frequency Fcmp having been set in the previous routine is 0, the control in the currently running routine is completed and the processing returns to the first start. If the drive frequency Fcmp having been set in the previous routine is not 0, it is determined that the drive frequency Fcmp has become 0 in the currently running routine, and the processing proceeds to the step S107. In the first routine immediately after the operation is turned on (YES in the step S101 for the first time), the previous value of the drive frequency Fcmp is set to "0" as its initial value.
In the step S106, it is determined whether the drive frequency Fcmp having been set in the previous routine is 0 or not. In other words, the controller 101 determines whether the compressor 1 is at the start-up or not by determining whether the drive frequency Fcmp which is 0 in the previous routine is no longer 0 in the currently running routine or not. If the drive frequency Fcmp having been set in the previous routine is 0 (YES in the step S106), it is determined that the compressor 1 needs to be started and the processing proceeds to the step S109. If the drive frequency Fcmp having been set in the previous routine is not 0 (NO in the step S106), it is determined that the compressor 1 has already been activated by the time of the currently running routine and is in operation, and the processing proceeds to the step S110.
In the step S107, the compressor 1 is stopped. At the same time as or in synchronization with this stoppage, in the subsequent step S108, the belt heater 7 is energized to start its heating operation, thereby the compressor 1 which is being stopped is heated.
In the step S109, compressor start-up control shown in Fig. 6 is executed. In the compressor start-up control of the present embodiment, as to the start-up of the compressor 1, temperature difference ΔTw corresponding to the difference between the respective detection signals of the inlet temperature sensor 111 and the outlet temperature sensor 112 is compared with a predetermined value ΔTsl, and the start-up of the compressor 1 is prohibited if the temperature difference ΔTw is equal to or larger than the predetermined value ΔTsl. The predetermined value ΔTsl is set as a temperature value within a range of about 3°C to 5°C.
In the step S110, the compressor 1 is operated at the drive frequency Fcmp.
In the compressor start-up control, in the step S201 of the flowchart shown in Fig. 6, the controller 101 calculates the temperature difference ΔTw between the inlet liquid temperature Twi and the outlet liquid temperature Two, and determines whether the temperature difference ΔTw is equal to or larger than the predetermined value ΔTsl or not. If the temperature difference ΔTw is equal to or larger than the predetermined value ΔTs1 (YES in the step S201), on the basis of the determination that there is no flow of the usage fluid in the first heat exchanger 2, the processing proceeds to the step S202 in which the compressor 1 is kept stopped. If the temperature difference ΔTw is smaller than the predetermined value ΔTs1 (NO in the step S201), on the basis of the determination that normal flow of the usage fluid is generated in the first heat exchanger 2, the processing proceeds to the step S209 in which the compressor 1 is activated. In other words, if the usage fluid is already flowing normally in the first heat exchanger 2 while the compressor 1 is stopped, the inlet liquid temperature Twi and the outlet liquid temperature Two become almost the same as the temperature of the usage fluid due to heat transfer from the usage fluid, and thus, it is determined to be normal.
The processing from the step S203 following the step S202 is processing of determining and displaying the abnormality after confirming whether it is definite that there is no flow of the usage fluid in the first heat exchanger 2.
In the step S203, the controller 101 determines whether a predetermined period has elapsed or not after the drive frequency Fcmp of the compressor 1 becomes 0, i.e., whether the state in which the temperature difference ΔTw is equal to or larger than the predetermined value ΔTsl has continued for the predetermined period or not. If the predetermined period has elapsed after the drive frequency Fcmp becomes 0 (YES in the step S203), the processing proceeds to the step S204. If the predetermined period has not elapsed (NO in step S203), the processing bypasses the processing from the step S204 and returns to the basic control routine shown in Fig. 5, and then after the control by the currently running routine is completed, the basic control routine is repeated. This is because the state of the usage fluid can only be accurately detected by the inlet liquid temperature Twi and the outlet liquid temperature Two after the compressor 1 has been stopped for a certain period of time.
In the step S204, the controller 101 adds 1 to a count value CNT (CNT=CNT+1).
In the step S205, the controller 101 determines whether the count value CNT after the addition has reached a predetermined value CNTa or not. In other words, erroneous determination due to a transient event is avoided by determining whether a situation in which the temperature difference ΔTw equal to or larger than the predetermined value ΔTsl is maintained for a predetermined period has occurred consecutively for the number of times determined by the predetermined value CNTa. If the count value CNT has reached the predetermined value CNTa (YES in the step S205), the processing proceeds to the step S206. If the count value CNT has not reached the predetermined value CNTa (NO in the step S205), the processing bypasses the processing from the step S206 and returns to the basic control routine. It is preferred that the predetermined value CNTa is about 3 to 5.
In the step S206, the controller 101 finally determines the first heat exchanger 2 to be under the condition where there is no flow of the usage fluid (hereinafter referred to as "abnormality determination"), and implements display or notification to prompt the user to recognize that the abnormality has occurred. For example, the screen of the display 114 is turned on to indicate the occurrence of the abnormality.
In the subsequent step S207, it is determined whether the user has performed a reset operation or not. If the reset operation is performed (YES in the step S207), the processing proceeds to the step S208. If the reset operation is not performed (NO in the step S207), the display of indicating the occurrence of the abnormality continues. In other words, until the reset operation is performed, the determination in the step S207 is repeated, and start-up of the compressor 1 is suspended. The reset operation can be performed by, for example, installing a reset button on the operation panel of the display 114. For example, after checking: the operation state of the pump installed in the external device; and occurrence/non-occurrence of clogging in the piping inside the first heat exchanger 2 or the piping in the external device, the user performs the reset operation only in the case where the check result shows no problem is confirmed.
In the step S208, the abnormality determination is canceled, the display of indicating the occurrence of the abnormality is stopped, the processing returns to the basic control routine, and the operation of the compressor 1 is enabled.
In the step S209, the compressor 1 is activated and operated at the drive frequency Fcmp having been set in the step S104 of the basic control routine shown in Fig. 5.
In the step S210 subsequent to the step S209, the compressor 1 does not need to be heated due to the start-up of the compressor 1, the belt heater 7 is de-energized and the processing returns to the basic control routine shown in Fig. 5.
Although the belt heater 7 is turned off in the step S210 after the start-up of the compressor 1 in order to reduce power consumption, the belt heater 7 may continue to operate in order to supplement the heat to be generated by the compressor 1 itself. In this case, the heat source unit U is always energized as long as it is connected to the power supply 11, and the heating of the compressor 1 by the belt heater 7 is continued.
Fig. 7 to Fig. 9 illustrate respective changes in the inlet liquid temperature Twi and the outlet liquid temperature Two for comparing temperature changes in different situations. Fig. 7 is a graph illustrating respective changes in the inlet liquid temperature Twi, the outlet liquid temperature Two, and the temperature difference ΔTw in the case of de-energizing the belt heater 7 under the condition where there is no flow of the usage fluid.
Fig. 8 is a graph illustrating respective changes in the inlet liquid temperature Twi, the outlet liquid temperature Two, and the temperature difference ΔTw when the condition of nonflowing usage fluid is maintained after starting to energize the belt heater 7 by continuing to stop the pump or by another means.
Fig. 9 is a graph illustrating respective changes in the inlet liquid temperature Twi, the outlet liquid temperature Two, the temperature difference ΔTw, and flow rate Rcw of the usage fluid when the pump is activated from the condition of nonflowing usage fluid and the circulation of the usage fluid via the first heat exchanger 2 is started.
In each of Fig. 7 to Fig. 9, the dotted line indicates the inlet liquid temperature Twi, the solid line indicates the outlet liquid temperature Two, and the two-dot chain line indicates the temperature difference ΔTw between the inlet liquid temperature Twi and the outlet liquid temperature Two. Further, in Fig. 9, the finer dotted line indicates the flow rate Rcw of the usage fluid.
In the machine chamber B inside the housing C of the heat source unit U of the present embodiment, the first heat exchanger 2 and the compressor 1 are disposed close to each other (Fig. 3) and the outlet of the usage fluid with respect to the first heat exchanger 2 is disposed above the inlet (Fig. 4), and thus the outlet temperature sensor 112 is in a higher position than the inlet temperature sensor 111 and thereby is larger in heat amount to be received than the inlet temperature sensor 111 by means of convection heat transfer, in which the belt heater 7 functions as the heat source. Hence, when there is no other thermal effect or when the other thermal effect exists but can be regarded as sufficiently small, the outlet liquid temperature Two as the temperature to be detected by the outlet temperature sensor 112 is higher than the inlet liquid temperature Twi as the temperature to be detected by the inlet temperature sensor 111. In the present embodiment, the temperature difference ΔTw is calculated as the difference obtained by subtracting the inlet liquid temperature Twi from the outlet liquid temperature Two (Two-Twi>0).
Referring to Fig. 7, when the belt heater 7 is de-energized and left as it is under the condition where there is no flow of the usage fluid (i.e., condition where the flow rate Rcw of the usage fluid is 0 [L/min]), the inlet liquid temperature Twi and the outlet liquid temperature Two tend to approach each other with the elapse of time and eventually converge to a temperature close to the outside air temperature.
Referring to Fig. 8, when the condition of nonflowing usage fluid is maintained after starting the energization of the belt heater 7 by continuing to stop the pump or by another means, the inlet liquid temperature Twi converges to a temperature value close to the outside air temperature whereas the outlet liquid temperature Two rises above the outside air temperature, thereby the temperature difference ΔTw occurs between the outlet liquid temperature Two and the inlet liquid temperature Twi, and the temperature difference ΔTw increases with the elapse of time and then eventually tends to converge while maintaining a constant difference.
Referring to Fig. 9, when: (i) the belt heater 7 is operated under the condition of nonflowing usage fluid and then is maintained in operation from the state where the temperature difference ΔTw is established between the inlet liquid temperature Twi and the outlet liquid temperature Two; and (ii) the pump is started at a time point t0 to start the circulation of the usage fluid via the first heat exchanger 2, the temperature difference ΔTw decreases with the elapse of time after the start of water flow (i.e., after the start of circulation of the usage fluid) and tends to converge to 0°C or its vicinity after elapse of a certain length of period.
As described above, when the belt heater 7 is operated without flow of the usage fluid, the heat to be discharged from the belt heater 7 warms up the air around the compressor 1 and thereby the ambient temperature inside the machine chamber B rises. Along with this heating, the outlet temperature sensor 112 in the upper portion of the machine chamber B and its installation location are also warmed up mainly by convective heat transfer. Since there is no flow of the usage fluid and the usage fluid stagnate before and after the first heat exchanger 2, the heat amount received from the belt heater 7 is retained at the outlet temperature sensor 112 and its installation location, and consequently, the temperature of the outlet temperature sensor 112 and its installation location rises so as to reach a temperature higher than the outside air temperature. Contrastively, the inlet temperature sensor 111 in the lower portion of the machine chamber B and its installation location are located near the bottommost portion of the installation region of the belt heater 7, thus are insusceptible to the heat radiation from the belt heater 7, and consequently maintain a temperature close to the outside air temperature.
When there is flow of the usage fluid in the first heat exchanger 2 during the shutdown period of the compressor 1, both the inlet temperature sensor 111 and the outlet temperature sensor 112 receive a large amount of heat transfer from the usage fluid in terms of heat capacity, and the influence of heat radiation from the belt heater 7 becomes relatively small. As a result, the inlet liquid temperature Twi to be detected by the inlet temperature sensor 111 and the outlet liquid temperature Two to be detected by the outlet temperature sensor 112 approach the temperature of the usage fluid and become substantially the same temperature. Accordingly, the temperature difference ΔTw between the outlet liquid temperature Two and the inlet liquid temperature Twi drops to 0°C or a temperature close to 0°C and becomes smaller than the setting value ΔTsl.
The heat source unit U according to the present embodiment has the above-described configuration. The effects to be obtained by the present embodiment are described below.
According to the present embodiment, the condition of non-flowing usage fluid, e.g., the condition where the pump of the external device is stopped, can be determined, without depending on an external input such as a signal from a pump interlock mechanism, by focusing on transition of the temperature difference ΔTw between the inlet liquid temperature Twi and the outlet liquid temperature Two during operation of the belt heater 7, specifically, by: detecting the temperature difference ΔTw between the inlet liquid temperature Twi and the outlet liquid temperature Two; and comparing the temperature difference ΔTw with the preset value ΔTsl. Further, the addition of special parts such as a flow rate sensor for detecting the flow of the usage fluid is not required, and thus, increase in number of parts can be suppressed or the number of parts can be reduced.
Therefore, by activating the compressor 1 under the condition where there is no commensurate difference between the temperatures Twi and Two detected by the inlet temperature sensor 111 and the outlet temperature sensor 112, it is possible to prohibit the start-up of the compressor 1 under the condition of nonflowing usage fluid. Thus, more appropriate protection of the heat source unit U can be achieved by complementing the pump interlock mechanism if the pump interlock mechanism is provided, or by not depending on the pump interlock mechanism if the pump interlock mechanism is unprovided.
Further, adjustment of the predetermined value ΔTsl to be compared with the temperature difference ΔTw enables detection of the condition where the flow rate Rcw is extremely small despite presence of flow in the usage fluid, for example, detection of occurrence of a problem such as leakage in the inlet pipe p1 and the outlet pipe p2 of the usage fluid.
According to the present embodiment as described above, without depending on the so-called pump interlock mechanism, the start-up of the compressor 1 is prohibited under the condition of nonflowing usage fluid or under the condition of extremely small flow rate despite presence of flow, and the heat source unit U can be protected from excessive load and/or freezing of its components or parts.
The inlet temperature sensor 111 and outlet temperature sensor 112 are essential sensors for various control operations of the heat source unit U, and utilizing such existing parts enables protection of the entirety of the heat source unit U without adding new parts.
Moreover, according to the present embodiment, the outlet of the usage fluid with respect to the first heat exchanger 2 is disposed above the inlet such that the heat amount to be received by the outlet or the outlet temperature sensor 112 from heat radiation from the belt heater 7 becomes larger than the heat amount to be received by the inlet or the inlet temperature sensor 111, and thus, the value that the temperature difference ΔTw should be can be clearly distinguished between the case where the usage fluid is flowing and the case where the usage fluid is not flowing.
In the above description, the outlet temperature sensor 112 is disposed above the inlet temperature sensor 111 to cause the difference between the inlet temperature sensor 111 and the outlet temperature sensor 112 in terms of heat amount to be received by convection heat transfer in which the belt heater 7 functions as the heat source.
The cause of the difference in heat amount to be received by the inlet temperature sensor 111 and the outlet temperature sensor 112 is not limited to the above-described configuration. The inlet temperature sensor 111 and the outlet temperature sensor 112 may be configured to differ in heat amount to be received by heat radiation from the belt heater 7. For example, the inlet temperature sensor 111 and the outlet temperature sensor 112 may be disposed so that the outlet temperature sensor 112 is closer to the belt heater 7, and such disposition makes the heat amount to be received by the outlet temperature sensor 112 from heat radiation from the belt heater 7 larger than the heat amount to be received by the inlet temperature sensor 111.
The sensor disposition is not limited to disposition of increasing the heat amount to be received by the outlet temperature sensor 112 but may be disposition of increasing the heat amount to be received by the inlet temperature sensor 111. For example, the inlet temperature sensor 111 may be disposed above the outlet temperature sensor 112 or the inlet temperature sensor 111 may be disposed closer to the compressor 1 or the belt heater 7 than the outlet temperature sensor 112. As to the sensor disposition, it is satisfactory if the heat amount to be received from the belt heater 7 is made different between the inlet temperature sensor 111 and the outlet temperature sensor 112.
Furthermore, the heat amount to be received by the inlet temperature sensor 111 and the outlet temperature sensor 112 is not limited to the means of convective heat transfer and heat radiation but may be influenced by heat conduction from the belt heater 7. In other words, it is satisfactory if the difference between heat amount to be received by the inlet temperature sensor 111 and the outlet temperature sensor 112 is not eliminated by heat removal by the usage fluid having no substantial flow and is detectable as the temperature difference ΔTw.
Although a description has been given to the air-cooling type heat source unit U, a water-cooling type heat source unit can also be applied. In this case, not only the first heat exchanger 2 but also the second heat exchanger 3 also become water-refrigerant heat exchangers, making the fan F unnecessary. Further, the partition plate 9 inside the housing C also becomes unnecessary, and the compressor 1, the first heat exchanger 2, the second heat exchanger 3, and other refrigeration cycle components are housed in a single space inside the housing C.
Although not specified in the above description, the heat source unit U may be provided with the pump interlock mechanism or may not be provided with the same. The pump interlock mechanism is a mechanism that detects the operation state of the pump and prohibits the compressor 1 from operating or starting when the pump is stopped. A superimposed fail-safe system can be achieved by being provided with the pump interlock mechanism. In particular, if leakage or clogging occurs in the piping of the usage fluid and there is no substantial flow of the usage fluid despite a normal working state of the pump, though the operation of the compressor 1 cannot be prohibited by the pump interlock mechanism because the pump is in operation, the configuration of the present embodiment can overcome such a situation.
Although a description has been given of the case where the four-way valve 4 is installed in the heat source unit U and can supply cold water and/or hot water to the external device, not limited to such a configuration, the heat source unit U can be configured as a cold water generator or a hot water generator by omitting the four-way valve 4. In the heat source unit U configured as a cold water generator, the first heat exchanger 2 functions as an evaporator and the second heat exchanger 3 functions as a condenser. In the heat source unit U configured as a hot water generator, the first heat exchanger 2 functions as a condenser and the second heat exchanger 3 functions as an evaporator.
Furthermore, the system to which the heat source unit U is applied may have a circulatory configuration configured to circulate the usage fluid between itself and the external device or it may have an open configuration. For example, in the system applied with the circulatory configuration, the heat source unit U is supplied with the usage fluid such as water from the external device, then cools or heats this usage fluid by the first heat exchanger 2, and then supplies the cooled or heated usage fluid to the external device. The usage fluid subjected to temperature adjustment and used in the external device may be discarded after being used for other purposes or being subjected to heat recovery.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

REFERENCE SIGNS LIST

U: heat source unit
C: housing
A: fan chamber
B: machine chamber
1: compressor
2: first heat exchanger
3: second heat exchanger
7: belt heater
9: partition plate
p1: inlet pipe
p2: outlet pipe
11: power supply
101: controller
111: inlet temperature sensor
112: outlet temperature sensor
113: operation switch
115: relay

Claims

A heat source unit (U) comprising:
a compressor (1) configured to compress a refrigerant;

a heater (7) configured to heat the compressor (1);

a first heat exchanger (2) configured to exchange heat between the refrigerant and usage fluid;

a first temperature sensor (111) disposed on the first heat exchanger (2);

a second temperature sensor (112) disposed on the first heat exchanger (2) at a location that is different from the first temperature sensor (111) in terms of heat amount to be received by heat radiation from the heater (7); and

a controller (101) configured to prohibit start-up of the compressor (1) based on difference between temperature detected by the first temperature sensor (111) and temperature detected by the second temperature sensor (112).
The heat source unit (U) according to claim 1, further comprising a housing (C) that houses the compressor (1) and the first heat exchanger (2), wherein:
the heater (7) is disposed on an outer periphery of the compressor (1) in such a manner that the heater (7) can heat the compressor (1);

the first temperature sensor (111) is disposed at an inlet of the usage fluid with respect to the first heat exchanger (2);

the second temperature sensor (112) is disposed at an outlet of the usage fluid with respect to the first heat exchanger (2), the outlet being different from the inlet in terms of heat amount to be received by heat radiation from the heater (7); and

the controller (101) is configured to
acquire respective detection signals output from the first temperature sensor (111) and the second temperature sensor (112), and

prohibit start-up of the compressor (1) when temperature difference corresponding to difference between a detection signal of the first temperature sensor (111) and a detection signal of the second temperature sensor (112) is equal to or larger than a predetermined value during operation of the heater (7).
The heat source unit (U) according to claim 2, wherein the heater (7) is a belt heater wrapped around the compressor (1) .
The heat source unit (U) according to claim 2 or claim 3, wherein the inlet and the outlet are different in heat amount to be received from the heater (7) by being different in position in a height direction or distance from the heater (7) .
The heat source unit (U) according to claim 4, wherein the outlet is disposed higher than the inlet or closer to the heater (7) than the inlet.
The heat source unit (U) according to any one of claim 2 to claim 5, wherein:
the housing (C) has a partition plate (9) that partitions interior of the housing (C); and

the compressor (1) and the first heat exchanger (2) are housed in the same space partitioned by the partition plate (9).
The heat source unit (U) according to any one of claim 1 to claim 6, wherein the usage fluid is water.
The heat source unit (U) according to any one of claim 1 to claim 7, further comprising:
an expansion valve (5);

a second heat exchanger (3); and

refrigerant piping (6, 6a, 6b, 6c, 6d, 6e, 6f) arranged in such a manner that the refrigerant can be circulated between the compressor (1), the first heat exchanger (2), the expansion valve (5), and the second heat exchanger (3), wherein:
the first heat exchanger (2) is configured to cool the usage fluid by heat exchange with the refrigerant; and

the second heat exchanger (3) is configured to discharge heat from the refrigerant after the usage fluid is cooled by the refrigerant.