KR20080025411A - Venturi Ducts for Heat Transfer - Google Patents

Abstract

The heat pump consumes power to transfer heat from the heat source to the hotter heat sink. The present invention allows for the spontaneous transfer of heat from a heat source to a small jet that is locally cooled to a temperature lower than that of the heat source by a Bernoulli effect in a generally higher working fluid. The Bernoulli effect occurs in venturi-like ducts formed to maintain an accessory flow. In venturi, the flow temperature, velocity, pressure gradient, and nussel effect limit heat transfer to small portions that increase heat transfer, improving heat transfer efficiency. At this point, heat transfer is maximized by a thermally conductive grid extending across the venturi neck.

Description

Venturi ducts for heat transfer {VENTURI FOR HEAT TRANSFER}

The present invention relates to a heat pump, apparatus for transferring heat from a heat source to a higher temperature heat sink. More specifically, the present invention relates to a Bernoulli heat pump.

  The heat engine is a device for moving heat from the heat source toward the heat sink. Heat engines can be classified into two basic types according to the direction of heat movement. The heat spontaneously flows downward, ie to the cold side. Like the flow of water, this "downward" heat flow can be used to obtain mechanical work by internal combustion engines and the like. A device that moves heat "up" or to the hot side is called a heat pump. This heat pump inevitably consumes power. Refrigerators and air conditioners are examples of such heat pumps. Most heat pumps operate by varying the temperature of the working fluid 1 in a range including the temperature of the heat source and the heat sink. In this way, the heat can spontaneously flow from the heat source to the lower temperature of the heat source in the working fluid. Similarly, heat spontaneously flows from the portion of the working fluid that is higher in temperature than the heat sink. The required temperature change of the working fluid is generally affected by the compression and expansion of the working fluid.

In contrast, Bernoulli heat pumps convert random molecular motion (reflected from fluid temperature and pressure) into directional motion (reflected from macroscopic fluid flow) to obtain the required change in working fluid temperature (the distinction between random and directional motion is This is particularly evident in the statistical distribution of molecular velocities: random motion is the width of the distribution and directional motion is the average of the same distribution). As the flow cross section decreases, such as when the flow passes through a nozzle or venturi, the fluid spontaneously switches from random molecular motion to directional motion. The change in the connection of temperature density and pressure along with the cross-sectional area is called the Bernoulli principle. Power is consumed in compression, but not in Bernoulli. The energy conservation characteristic of Bernoulli conversion is the basic efficiency used in Bernoulli heat pumps.

Conventional heat pumps and Bernoulli heat pumps are compared to FIGS. 1A and 1B. As shown in FIG. 1A, a conventional heat pump consists of four basic components: a compressor 4, an expansion valve 7, a low temperature heat exchanger 3 and a high temperature heat exchanger 2. 1B shows that the Bernoulli heat pump merges the role of the expansion valve 7 and the low temperature heat exchanger 8 into a heat transferable venturi 8. Conventional systems require large pressure changes for relatively low working fluid flow rates, while Bernoulli heat pumps require smaller pressure changes at high working fluid flow rates. The compressor 4 component (see FIG. 1A) of the conventional system is thus replaced by a fan or blower 9 in a Bernoulli heat pump (see FIG. 1B). Conventional heat pumps, Bernoulli heat pumps, heat exchangers, compressors, blowers and venturis have all been described extensively. The present invention describes a new structure in which heat 3 can be efficiently transferred to the fluid flowing through the venturi. The importance of the present invention lies in the improved efficiency provided to Bernoulli heat pumps. The following discussion describes the problems of the prior art that the present invention can address and solve in this regard.

2 and 3 provide a basis for comparison of the present invention with prior art, including Bernoulli heat pumps. FIG. 1 shows the change in the connection of temperature, density, pressure, flow rate and cross-sectional area of a compressible gas with so-called one-dimensional flow. There is nothing new and controversial about this well-known and highly studied phenomenon. The change in the linkage of these properties of the flowing compressible fluid is presented here again as it compares each other's initial efforts to exploit Bernoulli conversion and also provides a concise basis for comparison with the present invention. The detail of any one of the four quantities that change together in one-dimensional flow suggests values for the other three quantities. 2 shows temperature, density, pressure and cross-sectional area associated with flow rate (squared of flow rate). The flow rate is given the corresponding dimensionless Mach number. The linear decrease in temperature with the square of the flow velocity is a direct result of energy conservation, ie the conversion of random kinetic energy into directional kinetic energy. It is not surprising that the flow velocity scale with the Bernoulli effect is the Mach number (ratio of two velocities). The amounts shown in FIG. 1 are normalized to their values in the stationary gas.

Figure 2 immediately shows US Patent No. 3,049,891 and other inventions and the relationship of the present invention. In U.S. Patent 3,049,891 the flow must be supersonic (the Mach number is greater than one). 2 shows that the gas temperature is really lower in supersonic flows. However, Figure 2 also shows that the temperature reduction by subsonic flow is more appropriate for many practical purposes. In this regard, it should be noted that the temperature scale in FIG. 2 is an absolute value. In other words, at a Mach 1 flow rate, for example, the gas temperature was reduced by 25%. For example, if the temperature of the stationary gas is 70 ° F, the temperature near the neck of the venturi to be Mach 1 is -60 ° F, which is lower than zero. The numerical values shown in FIG. 2 assume the isentropic flow of the complete gas characterized by the specific heat ratio (ie 5/3) of the monoatomic gas. The challenge for Bernoulli heat pumps, therefore, is not to produce sufficiently low temperatures, but to efficiently use the low temperatures that appear near the throat of venturis and even subsonic venturis.

The second direct implication of Figure 2 is that the power required to maintain high velocity flow in the venturi neck can be significant. The pressure near the venturi neck is approximately half of the pressure at the venturi inlet. If this pressure drop is not recovered by the diffuser (enlargement of the venturi), the potential efficiency of the Bernoulli heat pump will be reduced. In addition to the need for a diffuser, efficiency also requires maintaining a non-peelable flow in the diffuser. This requirement requires a very progressively expanding diffuser, a highly asymmetric venturi (a venturi with very different reductions and enlargements). Many documents related to the so-called "critical flow venturi" in the broad sense indicate that the half angle (the angle between the cone wall and the axis of symmetry) of a conical diffuser, for example, should be less than 10 degrees. The efficiency requirements of asymmetric venturis are not addressed. U.S. Patent Nos. 2,325,036, 2,441,279, and 3,200,607 describe Bernoulli heat pumps but do not mention the efficiency and role of the diffuser. The first two of these patents relate to aircraft technology, where the power consumed by a short diffuser is a negligible part of the available power.

The focus of the present invention relates to the third aspect of FIG. 2, which does not cover any of the above four patent documents. In particular, the relationship shown in FIG. 2 between the flow velocity and the flow cross-sectional area for the flow velocity near Mach 1 shows that the inverse of the area exceeds the maximum as the flow velocity increases. This maximum is the basis for the Laval nozzle. The other implication of this maximum is that as a function of distance along the Venturi axis, temperature, density and pressure all create a narrow dip near the venturi neck (where the reciprocal of the area is at its maximum). It is indicated. That is, as shown in FIG. 2, the temperature, density and flow rate all change greatly near Mach 1 but the cross-sectional area does not change. Thus, when considered as a function of distance along the Venturi axis, or equivalently as a function of cross-sectional area, temperature, density and pressure all show a strong decrease in the neck of the Venturi. The temperature change for a particular venturi shape 11, which is being studied a lot, is shown in FIG. 3 (changes in temperature, density, pressure and flow rate along the venturi axis are specified as a function of distance along the venturi axis). (Implicitly) given in Fig. 2. Fig. 3 is obtained by making the area change of the cross-sectional area so-called "annular-shaped critical flow venturi." In these devices, the reduced portion of the venturi is toric and the enlarged portion is conical). . If the venturi wall is thermally conductive outside of the sharply reduced region shown in FIG. 3, the venturi wall provides a heat path for heat transfer from the other side of the working fluid flow to the cold throat of the same flow. That is, the heat transferred to the neck of the working fluid flow comes from elsewhere in the same working fluid flow, so there is no net gain. There is no net gain, but sacrifice comes. Since the heat transferred to the working fluid flow is the sum of the heat (desired effect) transferred from the heat source flow and the heat transferred elsewhere in the working fluid flow, it can be seen that the desired heat transfer is directly reduced by heat transfer outside the abrupt reduction zone. . It is the focus of the present invention to limit the heat transfer between the working fluid and the venturi wall to the sharply reduced area shown in FIG. This limitation is not addressed in previous patent literature.

The importance of this effect is modified and augmented by four additional effects, the so-called Nusselt effect and three effects associated with the boundary layer. The Nussell effect is an increase in heat transfer at the fluid-solid interface by convection brought into fluid flow. Since the flow rate disappears at the interface, the heat transfer from the solid to the working fluid depends on the heat conduction. However, the flow of working fluid over the boundary layer sweeps away the heat transferred to the boundary layer by conduction (convection). In general, convection is much more effective than conduction. At the flow rate near Mach 1, the Nussel effect is large. For example, if the heat source is a slow flowing fluid, the area where heat is transferred to the working fluid may be much smaller than the area where heat is transferred from the heat source flow.

Two additional effects are related to the change in boundary layer thickness along the venturi wall. Heat transferred from the venturi wall to the working fluid must pass through the boundary layer of the working fluid flow. The boundary layer is the region of fluid flowing adjacent to the solid-fluid interface. Since the flow velocity disappears at this interface, the velocity of the working fluid flow changes rapidly near the interface. The narrow area where these changes occur is called the boundary layer. The temperature gradient and thus the conduction heat transfer is greatly increased where the boundary layer is thin. The thickness of the boundary layer is greatly influenced by the pressure gradient along the direction of the working fluid flow.

The first of the two boundary layer effects relates to the direction of the pressure gradient. As is well known, the so-called "reverse" (ie positive) pressure gradient makes the boundary layer thicker. There is a "reverse" pressure gradient in the venturi enlargement (diffuser).

In the general view that directly follows the Navier-Stokes equation in the venturi's curtailment, where the axial pressure gradient is forward, the thickness of the boundary layer is inversely proportional to the square root of the axial pressure gradient. The axial pressure gradient increases rapidly in the temperature drop zone. This further thinning of the boundary layer in the temperature abatement region creates a fourth motivation for limiting heat transfer to this region.

The fifth and final considerations affecting the efficiency of Bernoulli heat pumps are addressed in the present invention. In FIG. 3, the portion marked “heat transfer slice” in the venturi represents a portion in which the heat transfer condition is good in the Venturi axis. All of these are mostly characteristics of the working fluid flow. That is, temperature and axial pressure gradients are characteristic of the entire cross section of the working fluid flow, excluding the thin boundary layer around the cross section. Viscous losses occurring outside of the temperature abatement zone represent lossless gains. The focus of the present invention is to exploit the properties of the thin portion 10 marked " heat transfer " in the Venturi axis in FIG. 3 without causing viscous losses associated with the portion outside the abrupt area of FIG. 3 in the venturi. Accordingly, there are five issues related to the sudden decrease area of FIG. 3 which are not addressed in the prior art.

1.Nugels of heat transfer through the neck of the venturi boundary layer,

2. Undesirable heat transfer from elsewhere in the working fluid flow to the abatement zone.

3. The axial pressure gradient in the diffuser is not forward.

4. The magnitude of the forward pressure gradient at the part within the reduced part of the venturi in the steep decrease.

5. Efficiency deterioration due to viscosity loss in the portion of the boundary layer outside the temperature abatement zone of FIG.

None of the five challenges are addressed in the prior art.

At the end of the discussion of the relevant technology, I would say that the Bernoulli transition is energy conserving (no power consumption), but Bernoulli heat pumps are not permanent motion devices. First, according to the second law of thermodynamics, there is an increase in pure entropy that must be compensated for by reversible work when heat is added (3) and removed from the working fluid flow at different temperatures (2). Because of the effect of this second law, the " heat dissipation " arrow in FIGS. 1A and 1B is made larger than the corresponding " heat inflow " arrow. The power required to compensate for this entropy is proportional to the temperature difference at which heat is added and removed. The second, more quantitatively significant, flow rate change in the boundary layer suggests viscous dissipation, which must also be compensated for by reversible work. If the first effect is the main task, the Carnot efficiency will be close. A larger challenge is due to viscous dissipation in the boundary layer.

The present invention relates to a structure using the "heat transfer" zone shown in FIG. 3 and to a system using the structure. This structure is a venturi specifically designed to transfer heat efficiently to the fluid flowing through the venturi. The present invention utilizes two types of "heat transfer" zones. First, heat transfer is limited to heat transfer zones. Second, heat transfer within the heat transfer zone is maximized by the use of special fins within that heat transfer zone.

According to another aspect of the invention, the heat source delivered to the working fluid may be a flowing fluid, gas or liquid or may be non-fluid as in the case of heat generating electrical components. An important requirement for both fluid and non-fluid sources is that there must be a thermal conductor connecting the heat source to a narrow portion of the Venturi axis, which is designated as the “heat transfer” zone in FIG. 3.

According to another aspect of the invention, the power consumed is reduced by allowing the diffuser to expand very gradually in order to maintain an attached flow.

According to another aspect of the present invention, the venturi can be cascaded to obtain a larger capacity or a larger temperature difference.

According to another aspect of the present invention, the waveform of the venturi wall is obtained with multiple "heat transfer slices" within a single venturi.

According to another aspect of the invention the heat transfer rate to the working fluid can be continuously varied by varying the flow rate through the venturi.

According to another aspect of the invention, a system based on heat transfer venturi may be open or closed. That is, the system can drain the working fluid with added heat or circulate the working fluid optimized for heat transfer or other properties.

According to another aspect of the invention a system based on heat transfer venturi may be used to pump heat “down”. That is, the heat source, which is higher in temperature than the working fluid when it is stopped, is cooled by conduction. By flowing the working fluid, the nussel effect and convection can be used. Cooling is further enhanced as the working fluid flows through the venturi. Cooling is further enhanced as the working fluid flows through the heat transfer venturi.

As with other heat pump technologies, Bernoulli heat pumps can be used for heating or cooling purposes.

1A shows the components of a conventional heat pump.

1b shows the components of a Bernoulli heat pump.

2 shows the change in the connection of the flow rate, temperature, density, pressure and cross-sectional area of the laminar flow of a compressible gas.

3 shows a graph showing the axial temperature change in the venturi and the “heat transfer” region of the venturi, with the dashed line curve representing the shape of the corresponding venturi.

4 is a cross-sectional view of a heat transfer venturi according to one embodiment of the present invention.

5A is a cross-sectional view of a rectangular venturi taken in a “heat transfer” zone that includes a grid of thermally conductive fins across a heat transfer zone of a venturi according to one embodiment of the invention.

5B is a cross-sectional view of a non-rectangular venturi taken in a “heat transfer” zone that includes a grid of thermally conductive fins across the heat transfer zone of the venturi in accordance with one embodiment of the present invention.

6A is a cross-sectional view of multiple heat transfer venturis staged in parallel to obtain increased capacity in accordance with one embodiment of the present invention.

6B is a schematic of a number of heat transfer venturis staged in series to obtain increased capacity in accordance with one embodiment of the present invention.

7 is a cross-sectional view of a venturi comprising a corrugated wall and multiple “heat transfer” zones in accordance with one embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

1: working fluid, fluid to which heat is added by heat transfer

2: heat removed from the working fluid at a (higher) heat sink temperature

3: heat added to the working fluid at the (lower) heat source temperature

4: Compressor to increase working fluid temperature and pressure

5: high temperature heat exchanger transfers heat from working fluid to heat sink

6: low temperature heat exchanger that transfers heat from the heat source to the working fluid

7: expansion valve to reduce pressure of working fluid

8: Venturi, duct with varying cross section

9: Fan / Blower to Maintain Working Fluid Flow

10: Cross section with low pressure, temperature and density, large velocity and pressure gradient in venturi

11: cross-sectional area of a typical "critical flow venturi"

12: slow moving and relatively hot parts of the working fluid flow

13: Fast moving, relatively low temperature part of the working fluid flow

14: Accelerator with pressure gradient "non-forward" in working fluid flow

15: Part of the working fluid flow exiting the venturi with added heat in the "heat transfer" section of the venturi

16: Venturi Wall

17: Heat source fluid flowing into or out of the plane of the drawing

18: heat conductor transfers heat from the heat source flow to the working fluid flow

18: Thermally conductive fins transfer heat from the venturi to the working fluid flow

The present invention provides an improved heat transfer structure for use in Bernoulli heat pumps. Embodiments of this heat transfer structure are shown in FIGS. 4 to 7. All embodiments use the "heat transfer" zone of the venturi shown in FIG. 3. This heat transfer zone is used in two basic ways. First, heat transfer to the working fluid flowing through the venturi is limited to the "heat transfer" zone 10. Second, heat transfer in the “heat transfer” zone 10 is maximized by providing a thermally conductive fin that serves to increase the surface area available for heat transfer within the “heat transfer” zone of the Venturi.

FIG. 4 shows a first embodiment in which the heat transfer structure is in the form of an asymmetric venturi 16 (venturi with reduced and enlarged portions). The working fluid suffers a Bernoulli shift. The length of the arrow is for indicating the flow rate and the longer arrow is for the higher velocity. When the working fluid enters the venturi 12, the gas moves slowly and is relatively hot and relatively dense. As the cross-sectional area decreases, the flow rate must increase to maintain a constant mass flow rate. The energy required to increase the flow rate is obtained from the random kinetic energy reflected in the temperature as shown in FIG. 2 (the temperature is lowered in proportion to the change in the square of the flow rate, which is called the Bernoulli effect). Thus, as the gas flows through the venturi, the flow velocity increases until it reaches maximum (13) at the minimum cross-sectional area (the axial change in flow velocity is mirror image of the change in temperature shown in FIG. 3). As the cross-sectional area in the diffuser portion of the venturi begins to increase, the flow rate decreases as the gas flows toward the venturi outlet 15 (14), and the heat source flow (17) through the thermally conductive material (18) at the venturi outlet The temperature of the gas rises to the extent that heat is transferred from it. An important point in the present invention is that the exposure of the thermal conductor 18 to the working fluid is limited to the “heat transfer” zone 10 shown in FIG. 3. The venturi wall 16 is insulated everywhere outside of the “heat transfer” zone 10. In particular, this structure prevents unwanted heat transfer from other areas of the working fluid into the "heat transfer" zone 10 of the working fluid.

The heat source shown in FIG. 4 is a flowing fluid, which is illustratively selected. The nature of the heat source and its thermal coupling to the heat conductor 18 are quite arbitrary. What is unique about the present invention is that heat transfer to the working fluid is limited to the "heat transfer" zone 10.

The second basic component of the invention is an additional structure shown in an enlarged cross sectional view of the “heat transfer” zone of the venturi in FIG. 5. In FIG. 5, the “heat transfer” zone of the venturi is in the plane of the drawing as compared to FIG. The heat transfer to the working fluid here is augmented by thermally conductive fins 19 extending from the venturi wall 20 into the working fluid flow. It is common to use fins to increase heat exchange. In addition to this point, the unique point of the present invention is that the range of the fin is limited in the direction of flow, that is, the direction parallel to the axis of the venturi. The fins here are localized in the "heat transfer" zone 10. The pattern of pins used is quite arbitrary. 5A and 5B show fins extending across the venturi in the “heat transfer” zone 10 to intersect to form a grid 19. Useful visualization of this grid structure can be given with tennis rackets, apple corer and (planar) filter. 5A and 5B also serve to emphasize the randomness of the cross-sectional shape of the venturi. Many venturis have cylindrical symmetry, but this is not a requirement.

Another aspect of the invention relates to the cross-sectional shape of a thermally conductive fin. The cross-sectional shape of the pin is airfoil and is designed to minimize the aerodynamic drag applied to the working fluid flow by the pin. The generally large component of drag, the so-called "pressure" component, is negligibly small due to the aerodynamic cross-sectional shape of the pin. Unlike the more common airfoils, the thermally conductive fins of the present invention do not need to provide a lift and also do not need to change the angle of attack. Thus, the fin of the present invention can be thinner and can be oriented along the streamline of the working fluid flow, further reducing drag. In this regard a fixed airfoil arrangement is often used to suppress turbulence in duct flow.

Another design degree of freedom for the grid element is that it can change the cross section of the grid element as it moves away from the venturi wall. In this design degree of freedom there is a tradeoff between thermal conductivity and structural strength. To ensure structural strength, the area must be increased as the distance from the venturi wall increases. In the case of thermal conductivity, the opposite is true. Proper balance depends on the material used for the grid elements.

As with Bernoulli heat pumps that do not use the "heat transfer" zone, a number of heat transfer venturis of the present invention can be configured in parallel to obtain greater capacity or in series to obtain higher or lower temperatures. This configuration is shown in Figures 6a and 6b.

To reduce the drag and thus reduce the power required on the blower / fan mechanism (9) to maintain the working fluid flow, such as to optimize the cross section of the fin-grid to minimize turbulence and drag on the scale of the heat transfer zone. The shape of venturis, especially diffusers, can be optimized independently. A common requirement in this regard is that the cross-sectional area at the diffuser portion of the venturi must be enlarged very gradually to maintain the accessory flow. The accessory flow serves to minimize the maximum component of the aerodynamic drag, the so-called pressure drag, leaving only the smaller component associated with the loss of viscosity. It has been reported that 95% of the pressure drop needed to obtain Mach 1 flow has recovered.

Another design approach relates to the flow rate at which the present invention operates. In contrast to traditional heat pumps based on a phase change of the working fluid, the operating conditions of the Bernoulli heat pump can be changed easily and continuously. In particular, the flow rate of the heat sink flow and thus the temperature can be varied by varying the power provided to the blower maintaining the heat sink flow. An important implication regarding this degree of freedom is that conventional systems are inefficient at startup. In the Bernoulli heat pump including the present invention, the salt pumping speed can be continuously changed to effectively eliminate the starting transient and its inefficiency. For example, a blower that maintains working fluid flow can be controlled by a thermostat. The second benefit of continuous change and control is the increase in thermodynamically acceptable efficiency even at smaller temperature differences (Carno efficiency is inversely proportional to the temperature difference at which heat is pumped. Thus, the present invention provides efficiency gains associated with longer operation over smaller temperature differences. Gives.

Finally, Figure 7 shows a waveform venturi wall designed to create multiple "heat transfer" zones within a single venturi. That is, the venturi wall is insulated outside the “heat transfer” zone but there are a number of “heat transfer” zones as shown in FIG. 7.

* Term Definition *

Venturi : A fluid flow duct or channel whose cross-sectional area changes along the axis. At least one minimum local cross section exists when the cross section changes along the duct axis. Most venturis have diffuser zones whose cross-sectional area increases along the axis, but the definition of the present invention for venturi also includes nozzles with short or no diffuser zones. This extension allows the present invention to be applied to applications where power consumption is not important.

Working fluid : A fluid whose temperature changes locally so that heat can spontaneously flow into and out of the working fluid.

Working fluid flow : The flow of working fluid through the venturi structure.

Cross-sectional area : The area within a closed curve formed by the intersection of a plane perpendicular to the venturi axis with the venturi surface.

Heat transfer zone : A section near the Venturi neck between two planes perpendicular to the Venturi axis, characterized by low temperatures and high flow rates (see FIG. 3).

Fin : extends from a thermally conductive surface into a fluid flow adjacent to the surface and consists of a high thermally conductive material whose purpose is to increase the surface area available for heat transfer between the surface and the fluid flow while minimizing flow resistance. .

Diffuser : The portion of the venturi that monotonously increases in cross-section along the axis and flow direction.

Claims (17)

Solid heat transfer venturi duct structure that can direct fluid flow. The cross-sectional area of the duct varies along its axis, One or more minimum local cross sectional areas are present while the cross sectional area is changing, The walls of the duct are insulated except for one or more cross sections (slices) of the duct and the nature of the fluid flow (temperature and boundary layer thickness) in the cross section contributes to heat transfer from the duct wall to the fluid flow, A heat transfer venturi duct structure in which the thermally conductive portion of the duct is connected to a heat source through a thermal conductor. The heat transfer venturi duct structure of claim 1, comprising one or more thermally conductive fins extending into the interior of the duct structure from the thermally conductive portion of the duct wall. 3. The heat transfer venturi duct structure of claim 2, wherein the fins extend across the duct. 3. The heat transfer venturi duct structure of claim 2, wherein the plurality of thermally conductive fins form a thermally conductive grid within the thermally conductive cross-section of the duct. 3. The heat transfer venturi duct structure of claim 2, wherein the fin is formed to minimize aerodynamic drag on the fluid flowing through the heat transfer duct structure. 3. The heat transfer venturi duct structure of claim 2, wherein the fins are aligned with the streamline of the fluid flowing through the heat transfer duct structure to reduce drag on the fluid. 3. The heat transfer venturi duct structure of claim 2, wherein the cross sectional area of the fin decreases away from the venturi wall. The heat transfer venturi duct structure of claim 1, wherein the heat transfer rate is controlled by a change in pressure drop in the heat transfer duct structure. The heat transfer venturi duct structure of claim 1, comprising a diffuser. 10. The heat transfer venturi duct structure of claim 9, wherein the diffuser expands slowly enough to maintain an accessory flow. The heat transfer venturi duct structure of claim 1, wherein the duct discharges flow to its local surroundings. Bernoulli heat pump system Heat Source, Heat transfer venturi duct structure according to claim 1, A thermal connection between the heat source and the thermally conductive zone of the heat transfer venturi duct structure, Working fluid flowing in the heat transfer duct structure, A blower mechanism for maintaining a working fluid flow through the duct structure, and Bernoulli heat pump system comprising a duct structure for connecting the heat transfer venturi duct structure and the blower mechanism. 13. A Bernoulli heat pump system according to claim 12, wherein the temperature of the heat source is higher than the temperature of the working fluid. The method of claim 12, Heat Sink, A heat exchange mechanism for transferring heat from the working fluid flow to the heat sink, A duct structure connecting the blower mechanism to the heat exchange mechanism, and Bernoulli heat pump system further comprising a duct structure for connecting the heat exchange mechanism to the inlet of the heat transfer venturi duct structure. A method of transferring heat to a fluid flow, Maintaining a pressure drop that maintains fluid flow through the heat transfer venturi duct structure according to claim 1, Maintaining heat flow of the heat transfer slice of the heat transfer venturi duct structure to one or more thermally conductive cross-sections. The heat transfer venturi duct structure of claim 1, wherein the heat transfer rate between the duct wall and the fluid flow is controlled by a change in pressure drop. The heat transfer venturi duct structure of claim 1, wherein the heat conductor is exposed to the heat source with a surface area that is at least twice as large as when exposed to the fluid flow.

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