US1120781A - Thermo-electric heating and cooling body. - Google Patents

Description

W. W. B. ALTBNKIRCH & G. R. GEHLHOPP.

THERMO ELEGTRIG HEATING AND COOLING BODY. APPLICATION FILED APR. 3, 1912.

1,1 20,781. Patented Dec. 15, 1914.

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W. E. ALTENKIRGH & G. R. GEHLHOFF.

THERMO ELECTRIC HEATING'AND COOLING BODY. APPLICATION FILED APR. 3, 1912.

1 1 20,78 1 Patented Dec. 15, 1914.

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UNITED STATES PATENIOFFIOE.

WALDEMAR WILLY EDMUND ALTENKIRCH, 0F rnnnnnsnonr, NEAR BERLIN, AND

GEORG RICHARD GEHLHOFF, or DANZIG-LANGFUHR, GERMANY.

rnERMo-nmc'rmc HEATING AND COOLING BODY.

Specification 01' Letters Patent. .Patented Dec, 15 1914,

Application filed April 3, 1912. Serial No. 688,298 7 To all whom it may concern:

Be it known that we, WALDEMAR WILLY EDMUND ALTENKIRCH and GEORG RICHARD GEIILHOFF, both subjects of the German Emperor, and residents of Fredersdorf, near Berlin, and Danzig-Langfuhr, respectively, Germany, have invented certain new and useful Improvements in Thermo-Electric Heating and Cooling Bodies, of which the following is a specification.

When an electric current is sent through a thermoelectric couple, as' is well known, the one junction is heated and the other cooled. It has heretofore been proposed to employ this effect, named after its discoverer, Peltier, for cooling railway cars for example. Such attempts must, however, necessarily fail, particularlyin the case of a low thermoelectric power of the substances employed, and owing to the great thermic conductivity of the thermoelectrically operative substances in the arrangement of thermoelectric couples known heretofore which admit of only small reductions of temperature being obtained, in the case of copper and iron, for example, not even 2 centigrade. Even though a thermoelectric cooling apparatus cannot have the efliciency of modern mechanical refrigerating plants, such a thermoelectric cooling apparatus would, however, be very suitable for household requirements and the like in consequence of its hygienic advantages, its absence of nolse and smell, its simple manipulatlon and constant readiness for operation. An arrangementis therefore described hereinafter which admits of producing any desired reduction of temperature starting from a given temperature of the cooling medium.

The idea on which the subject matter of the invention is based is the consideration that the heating effect of a thermoelectric couple through which an electric current is sent is always greater than the cooling effect. .Therefore, in order to obtain a favorable utilization of the heating and cooling effects while simultaneously using as little material as possible, not only must the hot junction be made larger than the cold, preferably in such a ratio that the superficial areas .of the' surfaces are approximately proportional to the ratio of the heating and cooling action,but the section from the hot to the cold junction must taper down correspondingly.

If the sections of the individual couples were made equal throughout and the superficial area at the hot junction were made as great as the heating eflect demands, the amount of material required to constitute a couple would increase in the ratio of the square of the superficial area of the elements. Such a couple would be very ineflicient. In addition, those substances of high thermoelectric power which are specially valuable for the present invention are more or less expensive. Therefore, a form of the couple which tapers down toward the cold junction will preferably be selected, for instance, a cone or wedge-shape, in order to keep the amount of material as low as possible. The junction may, in order to im-. prove the dissipation of the heat toward the outside, be cut open in known manner and connected with good conductors of heat, e. g., copper strips. Any desired number of such wedge-shaped couples may be arranged beside or behind one another for increasing the working voltage, thus obtaining the form of a hollow cylinder, for example, the hot junctions of which are located outside and the cold junctions of which are located inside. Moreover, if the operative substances are arranged alternately between metal rings or tubes of any desired section (annular, polygonal, corrugated or elliptical and so on) so that the couples attain the form of closed hollow rings, any desired ratio between the hot and cold surfaces can be readily obtained. Furthermore, such a body can be easily manufactured even in case it is made of brittle and fragile material and it is very durable. Now since the conductivity of heat of the various substances varies, the substances must be given different sections to enable a good cooling effect to be obtained.

In the case of cylindrical bodies the section can be changed by changing the thickness of wall of the operative substances. For a couple of bismuth and antimony the most favorable conditions are reached when the ratio of the section of bismuth to the antimony is 2.46 to 1. y

In the accompanying drawing which illustrates the invention, similar letters refer to similar parts throughout the several views.

Figure 1 is a longitudinal section of'aheating and cooling body of cylindrical shape. Fig. 2 is a diagrammatic view of an' a paratus embodying the invention, and Fig. 3 is a longitudinal-section of a modification of the form shown in Fig. 1.

The annular, positive, operative bodies (such as antimony) are designated a, and the negative (say bismuth) b,'c, designates metal rings (copper) and d insulating disks (paper, mica and the like). The poles or leads for the current are arranged at +6 and -e. Such a tube can be very easily manufactured, for example, the substances can be cast between the staggered metal rings or even be pressed in them when in a powdered condition. If desired, the outer copper rings may be heated and pushed over the previously preparedmembers, so that they firmly encircle the latter when'cooling down, or theusual soldering method, galvanization, or amalgamating may be employed, and so on. The inner copper rings may be inserted in similar manner after being cooled. 'By means of these couples of cylindrical, polygonal, elliptical and similar shapes all losses with the exception of the unavoidable losses due to the inner conduction of heat are almost completely avoided.

It is very important that the absorption of the heat should take place exclusively at the coldest part of the couple and the delivery of heat at the warmest part, and that no exchange of heat should take place between them, the space between the members bein completely filled with insulating materia Besides there is the additional advantage of the hot outer and cold inner junctions being completely separated, so that these may be at different pressures or be washed by various liquids.

If a cold liquid, 6. 9., salt water, be passed through the interior of the body, it is cooled on its way and can be led to a place at which it can absorb heat and thus exert a cooling effect. Such an arrangement is diagrammatically represented in Fig. 2. This arrangement would be suflicient, for example, if merely small quantities of ice are intended to be produced at considerably long intervals of time. The great heat absorbin power of the outer parts of the body su ces, in this event, for absorbing the heat produced for some time. Preferably, the inner junctions should be located as near as possible to the axis of the cylinder in order to reduce the heat absorbing power of the inner parts of the body as much as ,possible. The cooling then takes place very quickly. During the intervals or auses in working, the body may give off the lieat absorbed to the air to a suflicient extent. For increasing the conductivity of heat at the hot junctions, it is however, of advantage to cool the hot junction, for example by circulating li uids. If Sb (antimony) +25% Cd cadmium) be employed as the (bismuth) +10 tive alloy, and if the inner radius be 0, 5 cms. and the outer 3 cms. and the amount of the positive allo negative, it woul be necessary for keeping a cupboard cool that the cooling body be about 30 cms. high and that a current of 56 watts be consumed.

With a cooling body such as described only minor difl'erences in temperature can be produced particularly when the thermoelectric power of the substances employed is small and the consumption of current near gositive alloy and 90% Bi b (antimony) as the negabe 3.4 of that of the the critical temperature difference is rather considerable. By the aid of the following arrangement, however, any desired .reductlon 1n temperature can be obtained, starting .duced. For example, if the cylinder represented in Fig. 1 is surrounded by a second similar cylinder, the cold junctions of the second cylinder will be located directly next to the hot junctions of the first cylinder.

If the two cylinders are connected in par allel so that they must have the same voltage and number of couples, each individual junction or seam will, when the outer column is shifted for one member and the current changed correspondingly, have exactly the same potential and the same height as the corresponding next junction. It is consequently unnecessary to provide for insulation. Rather the same copper ring 0 may simultaneously constitute both the outer boundary for one couple of the inner cylinder and the inner boundary for the corresponding couple of the adjacent outer cylinder. The losses are thereby exceedingly small and at the same time any defects and inequalities in the material are automatically equalized by the inner distribution of current. Such a thermic cascade connection in the case of electric parallel connection is practicable not only in cylindrical couples. Though the form of the closed cylinder is very advantageous as regards durability, choice of material and avoidance of losses,

it is nevertheless not essential for the effect of this cascade connection, whether the rings are closed or whether they are subdivided the couples, and d are neutral disks serving for insulation. In this manner any desired number of such columns can be arranged one within the other.

The operation of this body is as follows: When a current is sent at +0 into this double row of couples connected in series parallel, a distributing of the current occurs. The strongest current passes through the outermost row of the thermoelectric couples because here it meets with the largest cross section, and the Weakest passes through the innermost row. Thus, a strong current fiows through each ring 0 inside this body from b to a of the outer column, and a weaker from a to b of the inner column. The stationary condition, which is created in this body, is such that on each double junction owing to the Peltier-efi'ect of that element or couple traversed by the stronger current is produced such as excess of cold, as is necessary for neutralizing the heat given on the next following junction.

The total difierence of temperature produced is, however, for 3 couples for example 3 times as great and at 71. couples n times as great as that produced in each individual couple, because in consequence of the exceedingly great transmission of heat obtained by the arrangement described between the junction of contiguous couples the temperatures of these junctions cannot be materially different one from another. If for certain substances there is a temperature diiference of 4 centigrade between the hot and cold junction and if the temperature of the outer hot junction is maintained constant at 6 C. by cold water, the cold junction of the outer body will have a temperature of 2 C. The hot junction of the second body contacting with it, the cold junction of which then is at 2 C. has the same temperature etc. Theoretically, there is absolutely no limitation to this process, so that by increasing the number of columns even for small thermoelectric powers, though in this case with very great consumption of energy and cooling water, it is possible to obtain any desired diminution of temperature from a given temperature of the cooling medium. The larger the number of such columns that are connected one with another, the less the consumption of energy, in the case of the higher attainablethermoelectric powers for not very great temperature differences the best results are approximately obtained with quite a small number, say two or three columns, connected one within the other.

Particularly for small thermoelectric powers it is most advantageous when the differences in temperature of one column is approximately equal to that of the column connected therewith in parallel. For this purpose the resistance of each outer column is made smaller than that of the preceding approximately in the ratio of the heating effect to the cooling effect of the innercolumn. For instance when the total cross section of the couples is constant the length of each couple must be smaller in the said ratio. The couples having the lowest temperature are the longest.

WVith the same material as mentioned in the above specified example, the internal radius of a double body is 1.1 cm. the intermediate radius 3 cms. and the other 5 cms. Accordingly, for keeping one cupboard cool a total height of about 15 cms. is required and an efliciency of current of 38 watts.

The body requires strong currents but very low voltages. It therefore can be operated by a branch of any main conductor, whereby the economy of operation is increased still further.

' Now since the production of heat at the outer hot junction is always larger than the expenditure of energy by the amount of the cooling effect of the inner cold junction, this thermoelectric body is well adapted for heating, preparing hot water, etc., Whereby a saving of electric energy is obtained in comparison with heating by J oules system. It is greater the less the difference in temperature, and amounts for example, in the case of a thermoelectric power of 150-160 eifective microvolts and 10 C. temperature difference to about 50%. In the case of this reversible electric heating, it is obviously necessary to lead away the quantity of calories 'saved to the outer heat or to the cooling water, that is to say, to heat the cold junctions directly or indirectly by means of these natural sources of heat, if it is not possible to make simultaneous use of the cooling effect.

We claim:

1. A thermo-electric couple comprising annular elements forming the couples in combination with metal rings electrically connecting and covering the peripheries of the couples.

2. A thermo-electric couple comprising substantially annular elements forming the couples, in combination with metal rings shrunk onto the peripheral inner and outer surfaces of each pair of elements, forming both an electrical and a rigid mechanical connection for the elements.

3. In combination, a plurality of concentric thermo-electric couples, the hot joint of one couple being adjacent the cold joint of another couple.

4. In combination, a plurality of concentric, adjacent thermo-eleetric couples whose hot joints are of greater area than their cold joints, the larger hot joints of one couple being in conductive relation to the smaller cold joint of the adjacent couple.

6. A thermo-electric couple for cooling, comprising the two elements of the couple, having a cold junction of less area than the hot junction and means for passing a current of electricity through the couple.

'7. A thermo-electric heating and cooling body, comprising thermo-electric couples, junctions for the couplesythe surface of the heat yielding junctions being larger than the junctions absorbing heat at the ratio of the production of heat to the cooling effect.

8. A thermo-electric heating and coolin pile, composed of a plurality of heating and cooling couples connected in parallel to a source of electricity and disposed to contact with one another and to form outer and inner columns, the hot junction of-the inner couple arranged adjacent the cold junction of an outer couple, the resistance of each outer column being less than that of the preceding approximately in the ratio of the heating efi'ect to the cooling efl'ect of the inner column.

partly as my invention, I have signed my ,name in the presence of two subscribing Witnesses.

WALDEMAR WILLY EDMUND ALTENKIRCH- Witnesses:

WOLDEMAR HAUPT, HENRY HASPER.

In testimony that I claim the foregoing partly as my invention, I have signed my name in the presence of two subscribing witnesses.

GEORG"RICHARD GEHLHOFF, PHIL. DR. Witnesses:

WOLDEMAR HAUPT, HENRY HASPER.

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