Showing papers on "Thermoelectric effect published in 1987"

Thermoelectric Conversion by Thin-Layer Thermogalvanic Cells with Soluble Redox Couples

Abstract: Thermogalvanic cells containing a redox couple of [Fe(CN)6]4−⁄3− or Fe2+⁄3+ as an electroactive species were built for thermoelectric conversion from low-grade heat with a temperature less than 100 °C. The distance between high- and low-temperature electrodes was set to 1 mm in order to produce a high power density. Thermoelectric powers, inner resistances, and heat fluxes of the cells, which were placed horizontally (i.e. in which the temperature gradient was vertical) were measured under steady state conditions. Natural convection, which was induced by a temperature difference and current flowing in appropriate directions, produced lower inner resistances than those with no convection by several times. It had only a small effect on thermoelectric powers and heat-transfer coefficients. Thus, both the power densities and the thermal efficiencies increased by nearly one order of magnitude due to the convection. A power density of 2.6 W m−2 was obtained during steady state using a cell containing an aqueous...

Thermoelectric heat pump

Abstract: A thermoelectric heat pump having first and second substrates with first and second copper metalizations formed thereon. The first and second copper metalizations are coated with nickel for soldering with a 90-10 lead-antimony solder having a eutectic temperature of about 251 degrees Celsius to nickel plates coated on first and second ends of n-type and p-type thermoelectric elements. The n-type and p-type semiconductor elements are arranged in an array of rows and columns with alternatively n-type and p-type elements connected in series with a first n-type element having a lead for connection to first terminal of a dc power source and a last p-type element having a lead for connection to a second terminal of a dc power source. The solder being of a composition that is both chemically and physically inactive with respect to the thermoelectric material for preventing the formation of regions of poor thermoelectric characteristics in the thermoelectric material and electrical shorts on the thermoelectric material.

Thermoelectric heating and/or cooling system using liquid for heat exchange

Abstract: A water purification or filtration system supplies purified or filtered water into an unpressurized, heavily insulated reservoir. A thermoelectric module thermally coupled to the reservoir pumps heat into or out of the reservoir, heating or cooling the purified water. A flow director thermally coupled to the thermoelectric module "shapes" room temperature water, which may be brine wastewater produced by the purification system or tap water diverted from the main water line by an in-line flow restrictor into a thin sheet flowing through a thin passage in the flow directors. Pumped heat from the thermoelectric module thereby is efficiently absorbed by the thin sheets of water, which may be discharged into a drain. A sealed electric pump delivers purified or filtered cooled (or heated) water to a spigot in response to actuating of a control switch.

Encapsulated thermoelectric heat pump and method of manufacture

Abstract: An encapsulated thermoelectric heat pump, apparatus and method for manufacturing the encapsulated thermoelectric heat pump is disclosed. The encapsulated thermoelectric heat pump includes a plurality of spaced n-type and p-type thermoelectric elements arranged alternatively in rows and columns. The thermoelectric elements having opposing ends operatively connected to first and second metalized ceramic substrates. The first and second metalizations patterned to connect serially the thermoelectric elements. The space between the spaced thermoelectric elements is filled with a microballoon filled epoxy for substantially increasing the strength of the thermoelectric heat pump to withstand a stress of more than 2000 g's. The apparatus includes a mold cup holding the encapsulating material, a mold holding the thermoelectric heat pump mounted in the mold cup, and a vacuum means connected to the mold for drawing the encapsulating material upwardly through the spaces of the plurality of thermoelectric elements to fill the spaces for curing.

Electrical conductivity and thermoelectric power of amorphous Sb2Te3 thin films and amorphous-crystalline transition

Abstract: The results of electrical conductivity and thermoelectric studies on antimony telluride, a promising thermoelectric material, in the thin film state are reported. Films were vacuum-deposited on to clean glass substrates with thickness between 50 and 200 nm and studied in the temperature interval 300 to 470 K. On heating the as-grown films, there is a sharp fall both in the Seebeck coefficient and the electrical resistivity at around 340 to 370 K for all the films. This is attributed to an amorphous to crystalline transition, which is confirmed by X-ray diffractogram and electron diffraction patterns.[/p]

Thermoelectric signal characteristics and average interfacial temperatures in the machining of metals under geometrically defined conditions

Abstract: The Herbert/Gottwein dynamic thermocouple method of temperature measurement was applied in order to experimentally evaluate the average interfacial temperatures arising in the external cylindrical turning of aluminium, brass, mild steel and stainless steel using high speed steel cutting tools. A detailed investigation of the EMF signal generated was undertaken for purposes of explanation of the DC and AC components which arise and of the influence of the cutting tool condition on the EMF signal generated. The thermoelectric characteristics of each material in conjunction with HSS were determined by means of the furnace method of calibration. A critical appraisal of each phase associated with the dynamic thermocouple method of cutting temperature measurement is undertaken in this paper and interfacial temperatures under a wide range of machine setting parameters for each workpiece material are presented and discussed.

Combined photovoltaic-thermoelectric solar cell and solar cell array

Abstract: A solar cell (10) generates an electrical voltage with contributions from both photovoltaic and thermoelectric effects, when a high thermal gradient is impressed across a semiconductor p/n solar cell. To achieve a substantial thermoelectric voltage contribution, the front side (12) of the solar cell (10) is heated to an elevated temperature consistent with efficient operation of the photovoltaic mechanism of the solar cell, and the back side (14) of the solar cell (10) is cooled to a lower temperature. The magnitude of the thermoelectric voltage contribution is increased by reducing the coefficient of thermal conductivity of the solar cell material, by using face electrodes (24, 26) having the proper thermoelectric potentials in contact with the solar cell material, by increasing the light intensity and thence the heat input to the front side (12) of the solar cell (10) and by cooling the back side (14) of the solar cell (10). The preferred material of construction is gallium arsenide, and the solar cell can be mounted to receive concentrated sunlight on its front side and to be cooled on its back side by enhanced thermal radiation.

Thermoelectric field burner

Abstract: A liquid-fueled thermoelectric field burner operable in two modes, a start-up mode and a steady-state mode. A rechargeable battery backed up by a manually operated generator permits cold start-up of a preheat burner followed by operation of a main burner which provides heat to thermoelectric converters which operate to provide necessary power for steady-state operation. Cold start-up is facilitated by atomizing the liquid fuel for combustion in the preheat burner, and steady-state blue flame operation is enhanced by mixing vaporized fuel and preheated air for combustion in a main burner. The thermoelectric converters are cooled by air from a cooling blower.

Liquid‐phase epitaxial growth of very thick In1−xGaxAs layers with uniform composition by source‐current‐controlled method

Abstract: A source‐current‐controlled method for the continuous supply of solute elements into solutions during growth was developed. In this method, a continuous electric current is passed through a GaAs source material of the solute elements during growth and the source material is dissolved into the growth solution due to Peltier and Joule heating at the interface between the source material and the solution. This method was applied to the liquid‐phase epitaxial growth of In1−xGaxAs on InP. The temperature variation of the solution was directly measured by immersing a thermocouple in the solution and a temperature gradient of more than 6 °C could easily be obtained in the solution between the GaAs source material and the InP substrate. The amount of dissolved GaAs was measured as a function of the current density. Using these results, an optimum growth condition for the continuous supply of solute elements was determined, and an 80‐μm‐thick In0.54Ga0.46As layer with uniform composition (x=0.458±0.002) was obtained.

Determination of charge carriers in superconducting La-Ba-Cu-O by thermoelectric measurements.

Abstract: Majority-charge carriers in high-${T}_{c}$ superconducting La-Ba-Cu-O are shown to be positive (holelike) carriers as determined by thermoelectric measurements in the temperature range of 300 to 28 K, the superconducting transition temperature.

High‐temperature thin‐film Pt–Ir thermocouple with fast time response

Abstract: We have developed a thin‐film Pt–Ir thermocouple which exhibits bulklike thermoelectric behavior up to 790 °C, the highest temperature observed with thin‐film pure‐element thermocouples. Using a Q‐switched Nd:YAG laser and a signal averaging oscilloscope, its thermal response time was measured to be 60 ns. The ease of implementation in electronic devices coupled with the reproducibility over a wide temperature range make this thin‐film thermocouple well suited for monitoring instantaneous temperatures during device processing.

Thermoelectric solar cell

Abstract: A patent is claimed for a thermoelectric solar cell, together with two subclaims and two parallel claims. The technical problem to be solved is to obtain, by utilising solar energy, an effective low-voltage solar cell which can be used for the decomposition of water (hydrogen production) and desalination of water electrochemically by electrolysis. The solution is to construct a thermoelectric solar cell from thermoelectric elements connected in parallel and in series. The parallel connection can be replaced by using metal strips and the competing thermal conduction by thinner electrical connections between the contact pairs. The efficiency can be increased and the material requirement reduced by additionally using a collector in the form of an optical lens, in particular a Fresnel lens. The thermoelectric solar cell is to be used primarily for the electrolytic hydrolysis and desalination of water. Two parallel claims request as a patent the direct utilisation of solar energy by the use of an optical lens, in particular a Fresnel lens, for grilling and simmering foodstuffs.

Effect of high temperature annealing on the thermoelectric properties of GaP doped SiGe

Abstract: Silicon-germanium alloys doped with GaP are used for thermoelectric energy conversion in the temperature range 300-1000 C. The conversion efficiency depends on Z = S-squared/rho lambda, a material's parameter (the figure of merit), where S is the Seebeck coefficient, rho is the electrical resistivity and lambda is the thermal conductivity. The annealing of several samples in the temperature range of 1100-1300 C resulted in the power factor P (= S-squared/rho) increasing with increased annealing temperature. This increase in P was due to a decrease in rho which was not completely offset by a drop in S-squared suggesting that other changes besides that in the carrier concentration took place. SEM and EDX analysis of the samples indicated the formation of a Ga-P-Ge rich phase as a result of the annealing. It is speculated that this phase is associated with the improved properties. Several reasons which could account for the improvement in the power factor of annealed GaP doped SiGe are given.

Anomalous Seebeck Coefficient in Boron Carbides

Abstract: Boron carbides exhibit an anomalously large Seebeck coefficient with a temperature coefficient that is characteristic of polaronic hopping between inequivalent sites. The inequivalence in the sites is associated with disorder in the solid. The temperature dependence of the Seebeck coefficient for materials prepared by different techniques provides insight into the nature of the disorder.

Use of high‐Tc superconductors for the determination of absolute thermoelectric power

Abstract: The use of the recently discovered high‐Tc superconductors for purposes of precision determination of the absolute thermoelectric power is illustrated on commercially available wires of copper and Nb‐Ti. High‐Tc superconductors offer a wide range of temperatures where precision metrology can be carried out, and their unusually steep upper critical field allows for an accurate determination of the effect of magnetic field on the thermopower of test leads.

Thermoelectric frost collector for freezers

Abstract: A thermoelectric heat pump attached to a plate evaporator within the freezer compartment. The surface area of the thermoelectric device is maintained at a temperature substantially lower than the temperature of the evaporator plate during the cooling cycle. Accordingly, the majority of frost is collected on the thermoelectric surface area. Defrost is accomplished by reversing the voltage potential across the thermoelectric device and draining the water away in a suitable manner.

Device for obtaining water from air using the Peltier effect

Abstract: In order to obtain water from air, a device is proposed which is based on a thermoelectric process. It is characterised by the use of the Peltier effect. The device can be connected both to existing power distribution systems and to autonomous power generating and power storage systems. In conjunction with buildings/hot houses, the device permits the creation of a microclimate.

Thermoelectric module optimized for low temperature difference

Abstract: A structure for joining thermoelectric and heat exchange elements in series so that the combination can be operated as a heat pump, at an elevated voltage with high efficiency when transporting high heat flux levels across very small temperature differences.

Cation intersite distributions in iron-bearing minerals via electrical conductivity/seebeck effect

Abstract: The equilibrium high temperature cation intersite distributions in iron-bearing minerals which exhibit small polaron “hopping” conduction can be determined by a technique which combines electrical conductivity and Seebeck effect. The procedure is demonstrated for ferrospinels (Fe3O4) - FeAl2O4 and Fe3O4 - CoFe2O4) and applied to the olivine Fe2SiO4 - Mg2SiO4 system.

Thermoelectric and photoelectric generation device

Abstract: PURPOSE: To upgrade the conversion efficiency from thermal energy to radiation energy and improve its generation efficiency of electricity by lowering the temperature of a combustion exhaust gas and reducing the principal part of sensible heat difference to radiation energy on the upstream side having a low temperature heat receiving body when the combustion exhaust gas passes the inside of a radiator. CONSTITUTION: The radiator 3 made of a porus solid is centered in the thermoelectric and photoelectric generation part and a combustion chamber 19, a vacuum space (or air preheating space) 20, a photoelectric conversion element 5, a reflecting mirror 21, a cooling water path 22 are formed at the periphery of the radiator. The reflection mirror 21 allows a radiation energy having wavelengths which are not absorbed in the photoelectric conversion element 5 to return to the side of the radiator 3 and its radiator 3 is heated and then, heat retaining energy is produced. In other words, when the exhaust gas passes through the radiator 3, the temperature of its exhaust gas is lowered and also the principal part of sensible heat difference is reduced to the upstream side having a low temperature heat receiving body as radiation energy. As a result, the conversion efficiency from partial energy corresponding to the above reduced one to radiation energy is upgraded and the generation efficiency of electricity is improved. COPYRIGHT: (C)1988,JPO&Japio

Thermoelectric power of Y-Ba-Cu-O and Eu-Y-Ba-Cu-O.

Abstract: The temperature dependence of the thermoelectric powers of the high-temperature oxide superconductors Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub x/ and (Eu-Y)/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub x/ is reported. The sign of the dominant carriers in the normal state is observed to be positive. Well above the superconducting transition, the magnitude of the thermoelectric power is a weakly decreasing function of temperature.

Thermoelectric material for low temperature use and method of manufacturing the same

Abstract: This invention relates to a method of manufacturing thermoelectric material which has the steps of quenching a thermoelectric alloy in a molten state at a quenching rate higher than 103°C/sec into a membrane or powdery form and subjecting the membrane or powder to cold-forming or sintering. The thermoelectric alloy is a Bi-Sb series alloy having a composition represented by {(Bi100-x•SBx)100-y•EII y }100-z•EI z where E' represents a group III or group IV element, E "represents a group IV or group VI element, x represents a number of 5 -20, y represents an integer of 0 -20 and z represents a number of 0.05 - 10, respectively.

Transient thermoelectric effects in intercalation compounds MxTiS2 (M=3d transition metals)

Abstract: Simultaneous measurements of thermal diffusion processes of electrons and phonons in 1T‐TiS2 and intercalation compounds MxTiS2 (M=Mn, Fe, Co, and Ni; x=0.1–1/3) have been made in the temperature range 78–280 K using a pulsed laser‐induced ‘‘transient thermoelectric (TTE)’’ or photodiffusion effect. The initial stage of the decay curves of TTE voltage observed solely in TiS2 gives the electron‐hole recombination times τr, from which capture cross sections are evaluated. At the second stage, two relaxation times (τf and τs) are observed in all crystals; the fast and slow components are associated with the intra‐ and intervalley scatterings through electron‐phonon interactions, respectively. The evaluation of the final stage yields the thermal diffusion coefficient DT and thermal conductivity κ of these materials. The effect of intercalation of the guest 3d metals on these quantities is qualitatively discussed.

Lanthanide Refractory Semiconductors Based on the Th3P4 Structure

Abstract: The phase relationships and the important structural, electrical and thermal properties of the R3X4-R2X3 (where R = lanthanides and X = S, Se and Te) phases having the Th3P4 -type structure are reviewed. The room temperature electrical resistivity and Seebeck coefficient of these materials are independent of R and only slightly dependent on X, but critically dependent on the X:R ratio. The long term stability of these phases is also reviewed. Although these materials have good thermoelectric properties there are some problems which need to be solved before these phases can be utilized in thermoelectric devices. These problems include long term stability, higher than desirable thermal conductivities, and low electron mobilities.