Heat exchange machines

Abstract

A condensate dehumidifier comprises a casing (fig 5) defining an airflow path (fig 3), one or more electric motors 3, a first set of fins disposed in the airflow path and fixed to a first drive shaft portion (fig 5), and a second set of fins disposed in the airflow path downstream to the first set of fins and fixed to a second drive shaft portion. The first and second drive shaft portions are driven by the or each electric motor. The dehumidifier further comprises a refrigeration circuit comprising a refrigerant compressor 4, a refrigerant expansion valve 5, an evaporation loop and a condenser loop. The evaporation and condenser loops are provided at least in part by channels (fig 6A) extending through the interiors of the first set of fins and the second set of fins. The dehumidifier further comprises a water collection chamber or channel adjacent to the first set of fins (fig 2).

Description

Technical Field The present disclosure relates to heat exchange machines such as condensate dehumidifiers. Background Efficient heat absorption from ambient air is important for a range of devices including condensate dehumidifiers and air source heat pumps. Both condensate dehumidifiers and air source heat pumps comprise refrigerant cycles. When ambient air comes into contact with the condenser coils of the refrigerant cycle, the air is cooled (in case of a condensate dehumidifier, so that water condenses on the condenser coils; in case of an air source heat pump, to extract heat from the air). Conventionally fans are used to drive ambient air over the stationary condenser coils. Inefficiencies due to friction and flow mixing can lead to inevitable energy losses within the system and a high energy consumption. Thus, there is a continued need to provide improved techniques to efficiently absorb heat from ambient air to improve the energy efficiency of condensate dehumidifiers and other devices that use heat absorption from ambient air. Summary According to a first aspect of the present invention there is provided a condensate dehumidifier. The condensate dehumidifier comprises a casing defining an airflow path extending from an air inlet to an air outlet, one or more electric motors, a first set of fins disposed in the airflow path and fixed to a first drive shaft portion, and a second set of fins disposed in the airflow path downstream to the first set of fins and fixed to a second drive shaft portion. The first and second drive shaft portions are configured to be driven by the or each electric motor. The condensate dehumidifier further comprises a refrigeration circuit comprising a refrigerant compressor, a refrigerant expansion valve, an evaporation loop and a compression loop. The evaporation loop is provided at least in part by channels extending through the interiors of the first set of fins and the compression loop is provided at least in part by channels extending through the interiors of the second set of fins. The condensate dehumidifier further comprises a refrigerant fluid within the refrigeration circuit, and a water collection chamber or channel adjacent to the first set of fins. According to a second aspect of the present invention there is provided a wind turbine. The wind turbine comprises a rotatable shaft and a plurality of fins fixed to the shaft such that exposure of the turbine to wind causes the blades and the shaft to rotate. The shaft and the fins define internal channels permitting fluid flow between a fluid inlet and a fluid outlet such that heat is exchanged between a fluid flowing between the inlets and exterior surfaces of the fins. Brief Description of the Drawings Figure 1 is a diagrammatic illustration of a condensate dehumidifier according to an embodiment; Figures 2 and 3 are cross-sectional and isometric views (with a cut-away section) of the condensate dehumidifier of Figure 1; Figure 4 is an isometric view of an electric motor, a gear box, a shaft and a refrigerant compressor of the condensate dehumidifier of Figure 1; Figure 5 is an exploded view of the condensate dehumidifier of Figure 1; Figure 6A is an isometric view (with a cut-away section to show the internal structure) of an example fin of the condensate dehumidifier of Figure 1; Figure 6B is a cross-sectional plan view of a further example fin of the condensate dehumidifier of Figure 1; Figure 7 is a cross-sectional view of a condensate dehumidifier according to another embodiment; Figure 8 is a side view of a condenser and an evaporator of the condensate dehumidifier of Figure 7; Figure 9 is an isometric view of the condensate dehumidifier of Figure 7; Figures 10A, 10B and 10C are isometric views of example fins of the condensate dehumidifier of Figure 7; Figure 11 shows cross-sectional side and plan views of a condensate dehumidifier according to another embodiment; Figure 12 is an isometric view of the condensate dehumidifier of Figure 11; Figure 13 is an isometric view of a cylindrical rotor of the condensate dehumidifier of Figure 11; Figure 14 is an isometric view of radial fins of the cylindrical rotor of Figure 13; Figure 15 is cross-sectional plan view of a condensate dehumidifier according to another embodiment; Figures 16 is an isometric view of a wind turbine according an embodiment; Figures 17 is an isometric view of another wind turbine according an embodiment; Figure 18 illustrates flow streamlines of the wind turbine of Figure 16; and Figure 19 illustrates an application of the wind turbine of Figures 16 or 17. Detailed Description Figures 1 is a diagrammatic illustration of a condensate dehumidifier system (i.e. a system for reducing or maintaining the level of humidity in the air). The condensate dehumidifier system comprises a refrigrent circuit comprising an evaporator 1, a condenser 2, a compressor 4 and an expansion valve 5. The evaporator 1, condenser 2, compressor 4 and expansion valve 5 are coupled to a hub (driven by an electric motor 3) to rotate around a central axis of the condensate dehumidifier system. The aerodynamic design of the fins of the evaporator 1 and the condenser 2 enables the dehumidifier system to draw in external humid air and propel it through a generally axial flow path (illustrated by the dashed arrows in Figure 1) formed by the hub and an external casing (not shown). A gearbox 6 is used to provide different rotating speeds for the compressor 4 and the hub in case only one motor 3 is utilized to drive both the hub and the compressor 4. Figure 2 is a detailed view of the dehumidifier of Figure 1. After passing the inlet section of the dehumidifier, the air enters the evaporator section formed by a plurality of fins attached to and extending from the first part of the rotary hub, with a low temperature refrigerant circulating through the internal channels of the fins, so that the fins can extract water and remove heat from the air. The water condensed through the evaporator section drips away from the fins and the adjacent casing wall, and is collected by a water collection container. The low-temperature dry air is heated by the following condenser section, which consists of multiple fins attached to and extending from the second part of the rotary hub. The evaporator and condenser sections are linked by an expansion valve or a capillary tube. Figure 3 is an isometric view of the dehumidifier system. The external casing and the hub form a converging-diverging flow path, corresponding to the compression and evaporation functions of the fins, so that the air is accelerated and decelerated as it passes through the axial air passage. Such flow acceleration and deceleration enhance the convective heat transfer on the fin surfaces. The casing and fin system enlarges the diameter of the machine as they approach the outlet section, which can minimize the loss of kinetic energy. The dehumidifier system can also be designed as a circular straight duct. The rotating fins are designed for driving airflow while maximizing heat transfer and water extraction. This leads to an improved energy efficiency compared to conventional dehumidifier systems. Because there are no stationary surfaces and components except the motor body, the formation and adherence of frost are minimized, making the dehumidifier advantageous in colder conditions. This improvement in energy efficiency enables significant reductions in product size and weight while also minimizing the impact on the environment. Figures 4 and 5 are further isometric views of components of the dehumidifier system. As noted above, the electric motor is equipped with a gear system, allowing the refrigerant compressor body and the hub-fin system to rotate at different speeds. The compressor and the motor with the gear system can either be integrated and positioned between the evaporator and the condenser sections or separated. The dehumidifier system can also utilize two sets of motor system, one motor to drive the hub, and the other to drive the refrigerant compressor. Figures 6A and 6B illustrate examples of the fin design for the evaporator and the condenser. The fins are designed to have external shapes resembling thin aerofoils or featuring concave or convex curves with a consistent cross-section. The fins include multiple internal channels (as shown in Figure 6A). Alternatively, the fins may also be formed by arranging a set of thin-wall tubes aligned in either convex or concave curves, resulting in external surface features with repeating wave-like pattern (as shown in Figure 6B). Figures 7 to 9 illustrate a further embodiment of a condensate dehumidifier. The condensate dehumidifier system of Figures 7 to 9 comprises spiral-shaped fins. The axial air flow path is formed by the casing and a plurality of continuous spiral-shaped fins with internal fluid channels, attached to and extending from a rotatable hub. Multiple fins originate from the inlet section of the rotatable hub, continuously sweep along the hub, forming multiple flow turning path. The pitch and fin height may vary along the axial direction. The hub diameter can either remain constant or vary along the axial direction. As shown in Figure 9, the dehumidifier system comprises a generally cigar-shaped casing with a plurality of inlet slots at the entrance section, allowing air to enter the evaporator section from both axial and circumstantial directions. Figures 10A, 10B and 10C are isometric views of three examples of the spiral fin arrangement. The fins are designed to have external shapes resembling thin aerofoils or featuring streamline curves with a consistent cross-section, allowing efficiently propulsion of the air while maximizing heat transfer across their surfaces. They include multiple internal channels. Alternatively, they can be formed by arranging a set of thin-wall tubes aligned in either convex or concave curved shapes, resulting in external surface features with repeating wave-like patterns in axial and / or radial direction (as shown in Figures 10B and 10C, respectively). Figures 11 and 12 illustrate a further embodiment of a condensate dehumidifier. The condensate dehumidifier system of Figures 11 and 12 uses a drum-type cross-flow rotor design. Both evaporator and condenser use a cylindrical rotor with multiple forward curved blades with internal fluid channels. The blades and the casing create a cross-flow air path that allows the air to enter the dehumidifier radially and pass across the cylindrical rotor. After leaving the evaporator section, air is redirected to the condenser through a duct on top of the casing. The outlet is located at the opposite direction of the inlet. The directions of refrigerant flow within the dehumidifier are indicated by respective arrows in Figure 11, whilst the directions of air-flow are indicated in Figure 12 by respective arrows. Figures 13 and 14 are isometric views of the cross-flow impeller type evaporator or condenser unit. Multiple fins with internal channels are arranged radially, forming a cylindrical structure. Internal fluid passes through the internal channels within each fin, is subsequently collected, and redistributed by a hub chamber. Alternatively, the fluid can circulate multiple times through the internal channels of each fin. Additional surface features, such as dimples, riblets and various types of turbulence generators, can be arranged on the fin surface to enhance the external convective heat transfer. Figure 15 illustrates a cross-sectional plan view of a further embodiment of a condensate dehumidifier. In the dehumidifier system of Figure 15, the evaporator and the condenser are not aligned along a common axis: instead, they are aligned with respective horizontal axes (alternatively these axes could be vertical axis or indeed angled axes). As shown in Figure 15, humid air enters the evaporator unit placed at a lower location, and exits the dehumidifier after passing through the condenser unit at a higher location. The evaporator and the condenser are connected thought a capillary tube or expansion valve. Figures 16 and 17 are isometric views of two examples of a combined wind turbine and heat exchanger design concept. Internal fluid channels can be placed within the Archimedes spiral wind turbine blades shown in Figure 16, or the cross flow radial wind turbine blades shown in Figure 17. The skilled person will appreciate that such designs accommodate the evaporation loop of the evaporation-compression circuit within internal channels of the blades. To maximize the heat transfer capacity, the number of blades in this integrated design may be higher than that of a conventional wind turbine. Additional surface structures such as dimples, riblets and vortex generators, can be added to the blade surface to enhance the convection rate. The rotation direction and the speed of the wind turbine can be controlled by an electric motor / generator. The motor serves to supply the initial torque necessary for rotating the blades, and can also function as a generator to capture kinetic energy from the wind. When there is no wind or the wind speed is low, the motor can drive the system to extract thermal energy from the air at a controlled rotating speed. Although not shown in Figures 16 and 17, it is to be understood that a refrigeration circuit (comprising a refrigerant compressor, a refrigerant expansion valve, an evaporation loop and a compression loop) may be connected to the proposed wind turbine. More specifically, the evaporation loop of the refrigeration circuit may be provided at least in part by the internal fluid channels of blades of the wind turbine (i.e. the evaporation loop may extract heat from the wind impinging onto the blades of the wind turbine). The compression loop of the refrigeration circuit may be provided to release heat to a desired target (e.g. to heat a water reservoir). The compressor of the refrigeration circuit may be coupled to the shaft of the wind turbine so that rotation of the blades (e.g. when driven by the wind or by the electric motor / generator) drives the compressor. In other variations of the above-described wind turbine, the blades may be designed differently. For example, the wind turbine may comprise a type of spiral shaped blades with varying pitches, a Savonius rotor, a Darrieus rotor, Giromill blades, and / or mixed turbines. Figure 18 illustrates flow streamlines around an Archimedes spiral rotor with a high blade count, when it concurrently functions as a fan blower and a heat exchanger. Figure 18 illustrates that, when the rotor rotates in the opposite direction to a conventional wind turbine, ambient air can ingress the blade surface from both axial and radial directions, generating a large number of impingement flow patterns that maximize the local heat transfer rate. Figure 19 is a diagrammatic illustration of an integrated wind catcher and rotary heat exchanger with internal fluid design such as the above-described designs (in particular as illustrated in Figures 6A-B, 8, 10A-B, and 16 to 18). The wind can be redirected through a wind catcher (e.g. installed on a roof of a building) and air pipeline to a ground level location where a rotary heat exchanger can be used to harvest both kinetic and thermal energy from the air. The design concept allows integration with Heating, Ventilation, and Air Conditioning (HVAC) systems, such as air-to-water heat pumps and air conditioners. This integration utilizes both kinetic and thermal energy from the wind, so that the HVAC system requires less additional energy consumption from the grid. Achieving net-zero energy consumption is feasible by integrating the system with batteries or thermal storage.

Claims

1. A condensate dehumidifier comprising:a casing defining an airflow path extending from an air inlet to an air outlet;one or more electric motors;a first set of fins disposed in the airflow path and fixed to a first drive shaft portion;a second set of fins disposed in the airflow path downstream of the first set of fins and fixed to a second drive shaft portion;wherein the first and second drive shaft portions are configured to be driven by the or each electric motor;a refrigeration circuit comprising a refrigerant compressor, a refrigerant expansion valve, an evaporation loop and a compression loop, the evaporation loop being provided at least in part by channels extending through the interiors of the first set of fins and the compression loop being provided at least in part by channels extending through the interiors of the second set of fins;a refrigerant fluid within the refrigeration circuit; anda water collection chamber or channel adjacent to the first set of fins.

2. A condensate dehumidifier according to claim 1, wherein the first and second drive shaft portions are configured to rotate about a common axis.

3. A condensate dehumidifier according to claim 2, wherein the first drive shaft portion, the second drive shaft portion and the refrigerant compressor are driven by the same electric motor.

4. A condensate dehumidifier according to claim 3 and comprising a gear system coupledto the electric motor and to the refrigerant compressor, the gear system arranged to allow an inner body of the refrigerant compressor to rotate at a different speed than an outer body of the refrigerant compressor, the outer body of the refrigerant compressor being coupled to the first and second drive shaft portions.

5. A condensate dehumidifier according to any one of the preceding claims, wherein the refrigerant compressor is provided at an axial position between the first and second drive shaft portions.

6. A condensate dehumidifier according to any one of the preceding claims, wherein the first set of fins is configured such that rotation of the fins by the first drive shaft portion compresses and propels the air flow along the airflow path, and the second set of fins, providedaxially downstream of the first set of fins, is configured to extract energy from the airflow and impart at least a part of that energy to encourage rotation of the second drive shaft portion.

7. A condensate dehumidifier according to claim 6, wherein the casing defines the airflow path to have a converging-diverging shape to support compression of the airflow in an upstream section of the casing and expansion of the airflow in a downstream section of the casing, wherein the upstream section of the casing houses the first set of fins and the downstream section of the casing houses the second set of fins.

8. A condensate dehumidifier according to any one of the preceding claims, wherein the casing has a substantially tubular shape, the air inlet being formed by an axial aperture of the casing and by a plurality of radial apertures of the casing.

9. A condensate dehumidifier according to any one of the preceding claims, wherein fins of the first and / or the second set of fins extend spirally about the axis of the first and / or second drive shaft portions.

10. A condensate dehumidifier according to any one of the preceding claims, wherein the first and the second set of fins are arranged to form axial fans for propelling the air flow along the airflow path between the air inlet and the air outlet.

11. A condensate dehumidifier according to claim 1, wherein the first and second drive shaft portions are configured to rotate about different axes12. A condensate dehumidifier according to any one of the preceding claims, wherein each fin of the first set of fins comprises a plurality of thin wall tubes arranged side-by-side along a convex or concave shaped curve to provide at least part of the evaporation loop, and / or wherein each fin of the second set of fins comprises a plurality of thin wall tubes arranged side-by-side along a convex or concave shaped curve to provide at least part of the compression loop.

13. A condensate dehumidifier according to any one of the preceding claims, wherein the first and the second sets of fins are arranged to form tangential fans for propelling the air flow along the airflow path.

14. A condensate dehumidifier according to any one of the preceding claims, wherein the refrigerant expansion valve comprises a capillary tube providing fluid communication between the compression loop and the evaporation loop.

15. A heat exchanger comprising:a wind turbine comprising a rotatable shaft and a plurality of fins fixed to the shaft such that exposure of the turbine to moving air causes the blades and the shaft to rotate;a refrigeration circuit comprising a refrigerant compressor, a refrigerant expansion valve, an evaporation loop and a compression loop, the evaporation loop being provided at least in part by channels extending through the interiors of the plurality of fins.

16. A heat exchanger according to claim 15 and configured so that rotation of the shaft drives, directly or indirectly, operation of the refrigerant compressor.

17. A heat exchanger according to claim 16 and comprising an electric motor-generator operable in a motor mode and in a generator mode, the electric motor-generator arranged to rotate the shaft when operated in the motor mode, and to convert kinetic energy of the rotating shaft into electric energy when operated in the generator mode.10

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