DE102008028731A1 - Heat exchanger for heating low cold hydrogen for drive equipment of motor vehicle, has channel for running parallel to other set of channels, where hydrogen is made to flow through former channel when medium possesses higher temperature - Google Patents

Abstract

The exchanger has a channel (13) provided between channel/channels (2) and a heat distribution medium. The channel (13) runs parallel to the channel and/or channels (2). The low-cold hydrogen to be heated is made to flow through the channel (13) when the heat distribution medium possesses a higher temperature, and flow through the channel (13) is blocked at lower temperatures of the supplied heat distribution medium. The low-cold hydrogen is guided into the channel/channels (2) in a full material block (1).

Description

The invention relates to a heat exchanger for heating cryogenic cold taken from a cryogenic tank for supplying a vehicle drive unit by the cooling liquid as a heat transfer medium, which is guided around the substantially formed by a solid block heat exchanger, while the cryogenic hydrogen in at least one in the solid material of the heat exchanger provided channel is guided. The technical environment is next to the DE 10 2006 025 657 A1 and the WO85 / 01101 on the US 3,749,155 directed.

at on vehicles powered by hydrogen as an energy source, in which the hydrogen stored in the cryogenic state in a so-called. Kryotank must be gaseous or extracted from this tank even liquid hydrogen will be heated before marriage he eg. An internal combustion engine, which is used as a drive unit for the motor vehicle acts to be supplied for combustion can, cf. For example, the first-mentioned font. This said Heating may be preferred in heat exchange with the Coolant of the liquid-cooled Internal combustion engine, which here generally as a heat transfer medium referred to as. However, for this heat exchange no usual liquid-liquid heat exchanger be used because of such due to the extremely low temperature (s) of the cryogenic hydrogen, the heat transfer medium would freeze in the heat exchanger.

One in terms of its construction simpler and yet for the described general application case more reliable Heat exchanger can by a so-called. Solid material block, for example be formed substantially in the shape of a cylinder, in which for example, parallel to the cylinder axis extending Channels are, for example, provided in the form of holes through that of the first cold and in the heat exchanger to be heated hydrogen is passed. Around the outer wall of this (eg cylindrical) solid material block around the heat transfer medium leading to the required heat For example, spirally in suitable lines or in the mentioned Solid material block provided here so-called. Leitkanälen be led around, as for example in the second-mentioned font is shown.

In order to prevent the above-mentioned danger of freezing of the heat transfer medium, it is, for example, from the third third letter mentioned already known at a heat exchanger for a cryogenic fluid in such areas of the heat exchanger, in which this fluid is still extremely cold, a lower heat transfer allow between the fluid and the heat transfer medium than in other heat exchanger areas in which the fluid to be heated has already experienced some warming. The latter areas are in particular the so-called fluid outlet side, that is to say that section of the heat exchanger in which the hydrogen to be heated or then already sufficiently heated emerges from the heat exchanger. In this sense is mentioned in the US 3,749,155 a heat exchanger is shown in which in a fluid to be heated by a suitable metal structure leading circular cylindrical channel of constant diameter, a so-called mandrel introduced, which extends over virtually the entire channel length and from the fluid inlet side of the channel to Fluid outlet side of the channel towards an increasing diameter. The annular gap between the channel wall and this mandrel thus narrows, starting from a channel region which is further upstream with respect to the flow direction of the fluid and thus becomes colder, toward a channel region which is further downstream and thus warmer. Since the fluid free flow area has a larger area in a colder region of the channel than in a warmer channel region, the fluid flows at a slower rate in the colder region than in the warmer region. As a result, the heat transfer that can be achieved is lower in the colder channel region than in a warmer channel region located downstream thereof, which reduces the risk of the heat transfer medium freezing in the vicinity of the colder channel region.

At This point should be briefly defined, which below the brevity here physically exact due to the term "lower heat transfer" used to understand. As is known, heat can be generated by heat conduction, transmitted by heat radiation and by convection for each of these heat transfer types specific physical relationships with specific Influencing factors and coefficients apply. The above is about that in different areas of a heat exchanger with otherwise identical boundary conditions different amounts of heat or heat streams are transmitted or transmitted can be. A lower heat transfer is therefore synonymous with that under otherwise unchanged Boundary conditions transmit a smaller amount of heat can be.

Although in the mentioned US 3,749,155 shown principle to avoid a heat exchanger icing has proven principle, yet other advantageous designs for solving the described problem are possible to show the present invention has set itself the task.

The Solution of this task is for a heat diver according to the preamble of claim 1, characterized in that between the channel (s) carrying the hydrogen and the heat transfer medium at least one further essentially parallel to this channel (s) extending channel is provided, which only then to be heated low-temperature hydrogen is flowed through, if that the heat exchanger supplied heat transfer medium a higher Temperature possesses while flowing through this further channel at lower temperatures of the supplied Heat transfer agent is blocked (or prevented). Advantageous embodiments and further developments are content of the dependent claims.

It It was recognized that the described danger of freezing the Heat transfer agent or acting as such Coolant of the vehicle drive unit in any case, with reasonable interpretation of the heat exchanger practically can only be done if this coolant itself has a relatively low temperature. As you know, the Coolant of an internal combustion engine (as Fzg. Drive unit) Temperatures between the ambient temperature (namely at shutdown or short term after a longer Standstill break during operation of the internal combustion engine) and approx. 115 ° C accept. While freezing from relatively hotter Coolant (with, for example, 95 ° C) in the heat exchange with cryogenic hydrogen with suitable heat exchanger design can be practically ruled out, can coolant with a temperature of, for example, 10 ° C in the same heat exchanger thoroughly freeze. Therefore, it is proposed in an inventive Heat exchanger different channels for to provide the hydrogen to be heated, wherein at least one of these channels the heat transfer medium is relatively close, while at least one other channel further away from the heat transfer medium. by virtue of the longer heat transfer path in solid material block the heat exchanger thus passes from the latter channel a lower "amount of cold" to the heat transfer medium as the first-mentioned channel, the closer to the heat transfer medium lies. If so long as the heat transfer medium itself is relatively cold, only in the heat transfer medium further spaced channel to be heated hydrogen out is, while by a closer to the heat transfer medium lying channel no hydrogen flows, so the heat transfer medium is less Heat withdrawn, as if by the latter closer Channel also flowed hydrogen. Thus, by a Division of hydrogen according to the invention different channels, one of which is closer to the heat transfer medium lying channel at relatively cold heat transfer medium not is flowed through, a freezing of the cold heat transfer medium be effectively avoided.

One inventive heat exchanger can formed by a substantially cylindrical solid block of material be through which several to improve the heat transfer conditions always flowed through channels preferably in parallel to the cylinder axis. These are preferably with respect the cross-sectional area of the solid block rather central while several more prefer the hydrogen only at higher temperatures of the heat transfer medium through the solid block leading channels in essentially annular around the former channels can be arranged around. If in the latter, only at higher temperatures traversed channels however, d. H. even if no hydrogen flows through them, Hydrogen is, so this is the possible heat transfer from the rather central, always flowed through channels to Heat transfer medium desirably even further hampered, since initially more heat transfer must be done and the thermal conductivity of Hydrogen much lower than that of the solid material (the solid block of the heat exchanger) is. Reached this effect just described, if at relative cold heat transfer medium an inflow of hydrogen in the only at higher temperatures of the heat transfer medium traversed channels is possible while only one outflow of hydrogen from said Channels by means of suitable valves or the like. Prevented becomes.

It is known that, in conjunction with a desired removal of hydrogen from the cryotank, if necessary, heat must be introduced into the cryotank in order to generate a certain overpressure in it, with the aid of which hydrogen is conveyed out of the cryotank. This heat input can be done with heated in said heat exchanger hydrogen as a heat carrier. However, since such a transfer of heat for a removal of hydrogen from the cryotank is not constantly required, a corresponding circuit, the heated hydrogen in the cryotank or by a heat exchanger provided in this, not continuously, but only as needed operated. By means of suitably switched lines, hydrogen taken from the cryotank can then be first heated in a so-called primary heat exchanger and then passed through a heat exchanger provided in the cryotank in order to introduce a required amount of heat into the cryotank, after which the hydrogen heated in this cryotank heat exchanger passes through a so-called. Secondary heat exchanger is passed before it is fed to the Fzg.-drive unit for combustion. Alternatively, an independent circuit can be provided for an intended heat input into the cryotank, as shown in the first-mentioned document, for the but also a so-called. Secondary heat exchanger is needed.

present It is now proposed that the one defined in the previous paragraph Secondary heat exchanger by the one or only at higher temperatures of the heat transfer medium flowed through channel or channels is formed. After to the implementation of the present invention in an inventive Heat exchanger anyway a subdivision quasi in two heat exchanger areas is required, this subdivision advantageously for Providing a primary heat exchanger and a Secondary heat exchanger can be used.

Especially with regard to an even distribution of the heat transfer in individual quasi disk-shaped areas of the solid material block can this in the sense of an advantageous development actually be divided into individual slices, which in one or more so-called cleavage plane (s) on which the cylinder longitudinal axis of solid material block is perpendicular, slightly apart are spaced. In each said cleavage plane can thus also over the temperature is approximately uniform Distribution of the hydrogen to be heated over which has the channels carrying the hydrogen Cross-sectional area or at least the "central" cross-sectional area of the solid material block, of course by providing suitable ring seals or the like for it Care must be taken that there is no flow connection between the always flowed through hydrogen channels and those surrounding channels exist, which only at higher temperatures of the heat transfer medium be acted upon by flowing hydrogen.

For further explanation, reference is made to the attached schematic diagram, in which a heat exchanger according to the invention for heating cryogenic cold taken from a vehicle cryogenic tank hydrogen for supplying a vehicle drive unit is shown in a half section. This heat exchanger is through a circular cylindrical solid block 1 with here horizontally extending longitudinal axis 6 formed, in which several parallel to the longitudinal axis 6 and these relatively obvious channels 2 and further from the central longitudinal axis 6 spaced channels 13 which the channels 2 quasi ring-shaped, are provided, which can all lead to be heated cryogenic hydrogen from an inlet side to an outlet side of the heat exchanger. The channels 2 and the channels 13 is on the entrance side as well as on the exit side its own so-called distribution room 4E (Admission to the channels 2 ) respectively. 14E (Admission to the channels 13 ) such as 4A (Exit for the channels 2 respectively. 14a (Exit for the channels 13 ), Wherein all distribution rooms 4E . 4A . 14E . 14A at the respective end faces of the solid block of material 1 provided and by a suitably guided boundary wall 5 of the heat exchanger are limited. By means of suitably provided openings in the boundary wall, hydrogen can enter the distribution spaces 4E respectively. 14E initiated or from the distribution rooms 4A respectively. 14A be discharged.

While the said distribution spaces 4E . 14E respectively. 4A . 14A for the hydrogen to be heated substantially at the two end faces of the here circular cylindrical solid material block 1 (or the entire heat exchanger) are provided, are guide channels 9 for guiding the coolant acting as a heat transfer medium of a vehicle drive unit, which introduces the heat for heating the hydrogen in the heat exchanger, on the lateral surface of the circular cylindrical solid material block 1 intended. These guide channels 9 are around the outside wall of the solid block 1 For example, spirally guided around. A supply nozzle for these channels 9 or the heat transfer medium guided therein is denoted by the reference numeral 10a while a discharge nozzle is the reference numeral 10b wearing.

To prevent the heat transfer medium possibly in the guide channels 9 freezes, then, when this heat transfer medium itself is relatively cold, only those closer to the longitudinal axis 6 lying channels 2 flows through of cryogenic hydrogen, while the surrounding these quasi ring-shaped and therefore closer to the heat transfer medium or at the guide channels 9 lying channels 13 then not be flowed through by the cryogenic hydrogen. In contrast, the heat transfer medium has a sufficiently high temperature, so that a freezing of the same len in the Leitkanä 9 can be ruled out with certainty, so are the respect to the central cylinder longitudinal axis 6 further outside and thus closer to the heat transfer medium lying channels 13 flows through with hydrogen. In the former case, of course, a significantly lower heat transfer between the cryogenic hydrogen and the heat transfer medium than in the second case, so that in the former case, the heat transfer medium does not freeze despite its relatively low temperature, further carried out a sufficient heating for the supply to Fzg.-drive unit can. Figurut not shown is a suitably provided valve or the like. Which is controlled by an electronic control unit at low temperatures of the heat transfer medium is closed and then a leakage of hydrogen from the channels 13 and thus also prevents them from flowing through. In particular, such a valve at an already mentioned drain opening of the distribution chamber 14A be provided, it should be noted that quite a variety of details may differ from the above explanations designed without the content to leave the claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102006025657 A1 [0001]
• WO 85/01101 [0001]
• US 3749155 [0001, 0004, 0006]

Claims (4)

Heat exchanger for heating cryogenic cold taken from a cryogenic tank for supplying a vehicle drive unit by the cooling liquid as a heat transfer medium, which is substantially surrounded by a solid material block ( 1 ), while the cryogenic hydrogen in at least one in the solid material ( 1 ) of the heat exchanger channel ( 2 . 13 ), characterized in that between the channel or channels ( 2 ) and the heat transfer medium at least one further substantially parallel to this / this channel / channels extending channel ( 13 ) is provided, which is only flowed through by cryogenic hydrogen to be heated when the heat transfer medium supplied to the heat transfer medium has a higher temperature, while a flow through this further channel ( 13 ) is blocked at lower temperatures of the supplied heat transfer medium. Heat exchanger according to claim 1 with a substantially cylindrical solid material block ( 1 ), characterized in that several always flowed through channels ( 2 ) parallel to the cylinder axis ( 6 ) run and of several substantially annularly arranged only at higher temperatures of the heat transfer medium flowed through channels ( 13 ) are surrounded, but in which there is always hydrogen. Heat exchanger unit according to claim 1 or 2 with a secondary heat exchanger, which is integrated into a heating circuit through which the cryogenic hydrogen in the cryotank can be supplied with heat by heat exchanged with the heat transfer medium hydrogen, characterized in that the secondary heat exchanger by the channel or channels through which or only at higher temperatures of the heat transfer medium ( 13 ) is formed. Heat exchanger according to one of the preceding claims, characterized in that the solid material block ( 1 ) is subdivided into at least two individual slices, which in one or more so-called cleavage plane (s) on which the longitudinal axis of the cylinder ( 6 ) of the solid material block ( 1 ) is perpendicular, are slightly spaced from each other.