DE202007014238U1 - Device for heat transfer of a heatpipe condenser - Google Patents

Abstract

contraption for transmission the heat a heatpipe capacitor for Solar collectors in a heat transfer fluid, especially in vacuum tube solar collectors, where the solar radiation on a pipe or surface absorber falls and is absorbed by this and the heat generated by heat conduction to the evaporator section a heat pipe is transmitted, so that the heat transfer fluid at least partially evaporated and the steam in the heat pipe in Direction capacitor rises and condenses in this, wherein the vapor during condensation the heat of vaporization to the walls of the condenser gives off and the condensed heat transfer fluid by gravity or with the help of capillary structures again is returned to the evaporation area and one possible low thermal transfer resistance from the surface the recording of the capacitor with low thermal resistance comprehensive for the Condenser in the direction of the heat transfer fluid to be heated of the heating circuit or an intermediate storage circuit is achieved thereby that one possible large area contact between said surface and the heat transfer fluid to be heated is present, characterized in that the capacitor holder in the direction...

Description

The The invention relates to a device for transmitting to a heatpipe capacitor discharged and preferably collected by a vacuum solar collector Heat on a heat transfer fluid, the direct or indirect heat an application supplied.

Heatpipe vacuum tube collectors play in the collection of solar heat especially in residential buildings increasing role. The reason lies in the often strongly disintegrating Offer solar energy and its use in the household, especially with heating support is critical in the private sector. Will in the summer months the in heat collected by the solar collectors, since there is no need for heating, insufficient used, the solar collectors heat up to the so-called stagnation temperature, i.e. on the temperature at which without dissipating heat to a consumption system a balance of heat and heat dissipation of the collector to the environment. Especially with powerful Vacuum solar collector tubes the stagnation temperature is over 300 ° C, which causes damage Steam production can lead to the heating circuits. Also the heat transfer fluid, the usual contains an antifreeze is damaged, by being thermally decomposed. The reaction products can too Lead blockages and so that the system partially unusable.

in the Contrary to the described "directly flowed through" systems has a heat pipe no direct liquid contact with the heat transfer fluid the user group, since the heat collected in the collector in the Heat pipe is led to a capacitor. There the heat gets to the Cover walls of the Capacitor discharged and flows through this. The outer surface of the Condenser of the heat pipe can be directly in the heat transfer fluid a heat transfer circuit are located and over their surface becomes the heat usually over one Temporary storage of use supplied. This cycle towards User is referred to below as the storage circuit. Frequently becomes but a "dry" connection of the heat pipe selected where the capacitor is in a receptacle. The heat flow takes place here "dry" by contact of the Capacitor or over the air gap to the outer surface of the Capacitor receptacle, through the wall of the capacitor receptacle to inner surface the capacitor holder and from there into the heat transfer fluid of the storage circuit.

A Heatpipe to transfer solar heat works as follows: The heat collected by the absorber plates evaporates a liquid, which is located in the evaporator section of the heat pipe. The generated steam flows to the condenser and gives by condensation its heat of vaporization to the Capacitor wall off. The condensed carrier liquid of the heat pipe becomes by gravity or by means of a capillary structure in the evaporation area returned and is thus again the heat transport available within the heat pipe, so that the circuit is closed.

Becomes no heat at the condenser taken out, the system heats up until the entire evaporator liquid the heat pipe has evaporated. The capacitor is in this state practically no heat supplied there is no heat transporting steam flow exists more and the other heat transport mechanisms like thermal diffusion or heat conduction only very little heat transport. The fin. the absorber plate with heat transfer tube but continue to heat up to the stagnation, wherein the pressure in the heat pipe rises. In the steady state prevail in the evaporator part and in the condenser the same pressures. The Temperatures of evaporator section and condenser may increase however, differ significantly.

at proper sizing of the heatpipe can be achieved through this mechanism Design heat pipe systems intrinsically safe. They are then for the private one Benefit easy to handle, since damage caused by steam production and Crack products are avoided. In addition, can be broken Pipes with "dry" connection also at inflated System dry replaced and aligned to the sun.

Prior art of heat transfer

The first patent for a heat pipe was registered in 1942 by Gaugier. it happened, however no use. In 1963, the principle was George Grover rediscovered, which secured corresponding property rights.

It is known, according to the solar lexicon, a heat pipe with "dry" connection, in which a pipe can be exchanged without draining the heat transfer fluid.In the case of the "dry" connection, the capacitor is in a recording, to which the capacitor has a good thermal contact owns and the heat is transported via condensation on the condenser wall - air gap - wall of the condenser holder - heat transfer fluid of the storage circuit.

adversely at the dry connection are the large thermal resistances and thus reducing the efficiency of the solar collector. The capacitors The Heatpipes have in all current applications from this Basically in proportion to the heat transfer tube diameter the heatpipe a big one Diameter and are comparatively long to provide sufficient contact area. If the capacitor is too small, the efficiency drops the heatpipe system considerably, as large temperature drops occur. The disadvantage of the "dry" connection is beyond the fact that due to the larger diameter in relation to the heat transfer tube of the heat pipe of the condenser, the heat transfer fluid can not flow back unhindered, which decreases performance in the operation of the tube at small angles of inclination causes.

Known is also the same Source the "wet" connection. The capacitor is located directly at the "wet" connection in the heat transfer fluid of the circle (memory circle). The path of the heat flow and thus loss-making temperature waste are significantly reduced in the wet integration. adversely but is also in the "wet" connection the big required contact area to the heat transfer fluid of the memory circuit, so that here too an education in the Diameter big and relatively long Capacitor is required, resulting in the same power reductions, in the dry connection at angles below 25 ° causes and difficulties brings with the seal to the storage circuit with it.

adversely is about it addition, the need for training of seals and the fact that before the tube change the water of the storage circuit must be drained.

It is known after Laid-Open Publication No. 2719 255 A1 , Filing date 2.04.1977, a "solar energy collector" in the Heatpipekondensator and an absorber tube into each other and that the absorber tube is thermally insulated by a shell whose space is evacuated, the shell and the interface between the condenser and absorber tube are welded together or the absorber tube is located in a dewar vessel-like insulating vessel or as a third possibility, the inner tube of the Dewar flask itself is used as an absorber tube and the capacitor is attached by adhesive or gaskets on the Dewar vessel.

adversely in this invention, the very large diameter of the heat pipe, what a very sluggish thermal Behavior causes and the extremely complicated manufacturing process and the volatility of vacuum tight connections.

Known is according to patent PCT / CN 2005/000668, application 13.05.2005 a glass Vaccum heat pipe. The inventors are Yin Zhiqiang at all.

Remarkable in this invention, the entire heat pipe is completely off Glass is made, allowing for cost-effective thermosyphon systems is well suited.

adversely in this invention, they are due to the low compressive strength Of glass only in relatively low temperature ranges, used can be and that a dry connection a very high risk of breakage brings with it, since the glass walls of the capacitor due to the required good heat transfer relatively thin must be trained.

at the known solutions exist the disadvantages that either the production of the solar collector heatpipe tube extreme complicated or not permanently vacuum-tight or one the diameter the heat transfer tube excess condenser to the heat transfer tube vacuum-tight by welding or soldering must be attached, but the low inclination angle of the heat pipe in the application does not allow and this capacitor the automatic welding of the Absorber sheets hindered or in the case of Glasheatpipe only small Temperatures and pressures manageable or there is a high risk of breakage.

According to the invention the wake of the known solutions solved by a redesign of the device for heat transfer according to the protection claims.

If the sequence of thermal resistances is determined individually on the path of the heat flow, it is clear that 80% -90% of the total resistance, the transition resistance in the "dry" connection from the wall of the condenser uptake to the heat transfer fluid of the storage circuit emanates and in the "wet" connection, the transition from the condenser surface to the heat transfer fluid of the Memory circuit is effected.

In the case of the "dry" connection, according to the invention, the surface of the capacitor holder ( 1 ) by cooling fins ( 2 ), which protrude into the heat transfer fluid of the storage circuit, so enlarged that the thermal resistance is significantly reduced. Since the thermal resistances of the steps condensation - flow through the condenser wall, the air gap and the walls of the condenser intake are small in relation to the contact resistance condenser absorption - heat transfer fluid of the storage circuit, it is possible, the diameter of the condenser ( 3 ) so that it corresponds to the diameter of the heat transfer tube ( 4 ) corresponds or the leading out of the vacuum tube portion of the heat transfer tube can be used directly after filling with the evaporator liquid, evacuation and vacuum-tight closure as a capacitor ( 1 ).

Another design according to the invention with the aim of increasing the contact surface to the heat transfer fluid of the storage circuit using the possibility of the end of the heat transfer tube, as described above, is used as a capacitor is in 2 shown. Here the capacitor ( 5 ) is improved in its heat transfer effect in that an intermediate body ( 6 ) From a good heat conductive material, such as copper or aluminum, pushed onto the end of acting as a condenser heat transfer tube. But it is better to shrink the intermediate body on the capacitor to avoid an air gap.

In the case of wet connection according to the invention, the contact surface to the heat transfer fluid of the storage circuit is increased by the fact that in the manifold ( 8th ), to which the individual tube collectors are connected, for each tube a ribbed body ( 7 ) is made of highly conductive material and in which the unexpanded, as a capacitor ( 5 ) serving end of the heat transfer tube is pushed into ( 3 ).

embodiment

One Vacuum tube collects 70 W heat output with direct flow in the storage circuit. The efficiency eta 0 is 0.79. It will now the following cases examined:

1. more usual Capacitor 022 mm, length 48 mm

The individual thermal resistances and temperature drops result in: therm. resistance Temp. Waste K / W K Absorber plate heat transfer tube to neglect 0 Flow through pipe wall to neglect 0 Heat transfer tube wall-liquid 0.019 1.33 condensation 0,025 1.74 Flow through the condenser wall 7.77 E-4 0.05 Flow through the air gap 0,015 1.03 Flow through condenser intake 7.77 E-4 0.05 Heat transfer to storage circuit 0,366 25.6 total 29.8

With such a design, the efficiency decreases: eta 0 directly flowed through tube: 0.79 eta 0 selected heat pipe: 0.7

2. Heat transfer to 1

fin body : Surface to Heat carrier of the memory circuit 140 cm ² diameter of the capacitor : 10 mm Length of the capacitor 50 mm

Under this assumption, the following thermal resistances and temperature drops result: Therm. resistance Temp waste K / W K Absorber plate heat transfer tube to neglect 0 Flow through pipe wall to neglect 0 Heat carrier tube wall liquid 0.019 1.33 condensation 0,055 3.88 Flow through the condenser wall 6.8 E-4 0.05 Flow through air gap is eliminated 0 0 Flow through condenser intake 6.8 E-4 0.05 Heat transfer to storage circuit 0.088 6,156 11.4

Due to the significantly reduced total temperature drop, the following difference in efficiency is to be expected: eta 0 directly flowed through tube: 0.79 eta 0 known solution: 0.7 eta 0 at heat pipe according to Figure 1: 0.76

It It should be noted that despite in relation to the evaporator tube of Heatpipe unexpanded capacitor, the efficiency of the selected, inventive embodiment higher than in the known solutions is. About that In addition, the inclination angle of the heat pipe solar collector tube can be smaller chosen be what the applications elevated.

Claims (10)

Device for transmitting the heat of a Heatpipekondensators for solar collectors in a heat transfer fluid, especially in vacuum tube solar collectors, in which the solar radiation falls on a pipe or surface absorber and is absorbed by this and transfer the heat generated by heat conduction to the evaporator section of a heat pipe is so that the heat transfer fluid at least partially evaporated and the vapor rises in the heat pipe towards the condenser and condenses in this, wherein the vapor in the condensation, the heat of vaporization to the walls of the capacitor and the condensed heat transfer fluid by gravity or by means of capillary again is returned to the evaporation region and the lowest possible thermal transfer resistance from the surface of the capacitor with low thermal resistance comprehensive recording for the capacitor in the direction of aufzus heating heat transfer fluid of the heating circuit or an intermediate storage circuit is achieved by the largest possible contact between said surface and the heat transfer fluid to be heated is present, characterized in that the condenser receptacle is equipped in the direction dissipated heat with cooling fins with adequate area, where appropriate, at the same time turbulent flow is realized. Device for heat transfer a Heatpipekondensators according to the preamble of claim 1 thereby characterized in that the desired large area contact between the surface the capacitor holder in the direction of the heat transfer fluid to be heated caused by the fact that the capacitor surface by a complete or only partially the capacitor comprehensive coat of a material good thermal conductivity is enlarged. Device for heat transfer A heatpipe condenser according to claim 1, characterized that the cooling fins integrated in the distributor of the solar module. Device for heat transfer A heatpipe condenser according to claim 1, characterized that the surfaces the cooling fins the heatpipe are so big that it is not necessary, a specially expanded condenser head form, but the upper part of the evacuated and with an evaporator liquid filled Heat transfer tube protrudes directly into the heat pipe receptacle and thus the capacitor forms. Device for heat transfer A heatpipe condenser according to claim 2, characterized that said coat is so large is that it does not require a specially dilated Condenser head form, but the upper part of the evacuated and with an evaporator liquid partially filled Heat transfer tube directly into the heat transfer jacket protrudes and the unit from the upper part of the heat transfer tube the condensation region, and the jacket forms the condenser head. Device for heat transfer A heatpipe condenser according to claims 2 and 5, characterized that the jacket is made of solid copper or aluminum. Device for heat transfer A heatpipe condenser according to claims 2 and 5, characterized that the sheath of copper or aluminum receives recesses, the the coat a spokes wheel-like Shaping. Device for heat transfer A heatpipe condenser according to claim 1, characterized that in the case of a "wet" connection with a a big one surface equipped with cooling fins, for example body is in the distributor and that in this body the condenser of the heat pipe is inserted. Heat pipe heat transfer according to claim 8, characterized in that the capacitor from the Heat transfer tube is formed. Heat pipe heat transfer according to claim 1, characterized in that the heat sink so is designed to simultaneously record several heat pipes can.