Thermoelectric coolers

Several LED chips have been mounted together on the same thermoelectric cooler shown in Fig. 13.56b. This nondispersive IR analyzer utilizes sample and reference PbSe photoresistors as detecting elements. The LED emission (4.3 xm for CO2 and 4.7 xm for CO detection) is focused onto a sample photodetector by a concave mirror. 

Figure 11.1 (a) Scheme of an isoperibol titration calorimetry apparatus A Dewar vessel B lid C stirrer D electrical resistance E thermistor F titrant delivery tube G O-ring seal, (b) Vessel for isothermal operation A stainless-steel, platinum, or tantalum cup B water-tight stainless steel container C heater D Peltier thermoelectric cooler E O-ring seal F heater and cooler leads. Adapted from [211],... 

SEP standard error of prediction TE/TEC thermoelectric/thermoelectric cooler... 

Antimony alloys have many commercial applications. The metal makes its alloys hard and stiff and imparts resistance to corrosion. Such alloys are used in battery grids and parts, tank linings, pipes and pumps. The lead plates in the lead storage batteries constitute 94% lead and 6% antimony. Babbit metal, an alloy of antimony, tin, and copper is used to make antifriction machine bearings. Alloys made from very high purity grade antimony with indium, gallium and bismuth are used as infrared detectors, diodes, hall effect devices and thermoelectric coolers. 

The components of a thermoelectric cooler are indicated by the cross section of a typical unit shown in Fig. 1. Therm oelectiic coolers such as this are actually small heat pumps that operate on the physical principles well established over a century ago. Semiconductor materials with dissimilar characteristics are connected electrically in senes and thermally in parallel, so that two junctions are created. The semiconductor materials are n- and /i-type and are so named because either they have more electrons than necessary to complete a perfect molecular lattice structure (ri-type), or not enough electrons to complete a lattice structure (/7-type). The extra electrons in the -type material and the holes left in the /7-type material are called carriers and they are the agents that move the heat energy from the cold to the hot junction. 

Thermoelectric coolers find three basic categories of applications. (1) Use in electronic components (2) in temperature control units and (3) in medical and laboratory instruments. 

Applications requiring low-tcmpcraturc thermoelectric coolers usually have strict limitations on available power. Therefore, it is not practical to fabricate and stock numerous different cascades that can be optimized for only one set of conditions. On the other hand, fully optimized prototypes involve engineering and manufacturing costs that may prove uneconomical for some applications. Therefore, a low-cost alternative approach has been developed for responding to such requirements. Standard cascades are fabricated by assembling pcrtials of standard modules. The number of... 

The heat sink design is very important. The heat sink must carry heat away with minimum rise of temperature. It should be stressed that all the thermoelectric cooler does is to move energy from the load to the heat sink where it must be dissipated to another medium, the latter required to be cooler than the hot junction. 

Power supply capabilities for thermoelectric coolers range from the simple open-loop direct current supply with a switch to sophisticated feedback systems with close temperature regulation and fast response. The only limitation on the supply is that ripple be maintained at a point lower than 10 to 15%. Open-loop systems will generally contain a transformer, rectifiers, choke, and chassis with heat sink for the rectifiers. In feedback systems, a thermistor is used to sense temperature at the cold junction. This signal is compared with the desired temperature setting to obtain an error signal. 

Multipinned phase (MPP) is an electronic technique that significantly reduces the dark current, with some cost in the full well capacity. MPP devices exhibit dark currents that are 1 to 2 orders of magnitude lower than similar non-MPP CCDs at the same temperature. Conversely, an MPP CCD may be operated at higher temperature and exhibit as low a dark current as a much cooler non-MPP device. This feature is attractive when the user wants to avoid liquid nitrogen cooling. MPP CCDs cooled by an air-cooled thermoelectric cooler can easily exhibit dark currents in the region of 1 e /pixel/sec. 

In order to minimize noise and Li migration, the solid-state detector should be cooled, usually to 80 K. This can be done using liquid nitrogen but it is quite inconvenient to have a cryogenic container mounted on the detector arm, especially since the container needs to be refilled every few days. Thus, solid-state detectors coupled with thermoelectric coolers have been developed and commercialized, and successfully used in powder diffraction. 

A thermoelectric cooler with a ZT of 1 operates at only 10% of Carnot efficiency, whereas a thermoelectric cooler with a ZT of 4 would achieve 30% of Carnot efficiency, which is comparable to the efficiency of a home refrigerator. 

The number of integration time doublings, n, can be increased until either a time limitation imposed by the experiment is reached, or the integrated dark current exceeds 50% of saturation. The dark current can be reduced by cooling the LDA. The thermoelectric coolers used in our instrument cool the detector to a temperature of about -5 C which provides a maximum useful integration time of about 20 s. 

In order for a material to be an efficient thermoelectric cooler, it must possess a large thermoelectric figure of merit, Z, which is defined by equation 1. 

I, thermoelectric cooler J, small ball valves K, levelling device, (reproduced by permission from Costigan M... 

FOCUSING LENS AVALANCHE PHOTOOtOOE THERMOELECTRIC COOLER... 

Currently the most popular cooling method is the externally controlled passive cooling technique using traditional convection heat transfer and heat exchanging techniques such as fins [1], a fan [3], and compressed air for microfluidic device cooling. Integrated cooling techniques for microfluidic devices are very limited such as the Peltier thermoelectric cooler [2] and endothermic cooler [7] mentioned above. 

Dew/frost-point hygrometer - utilizing a chilled mirror surface. The mirror is maintained at the dew-point temperature by automatically controlling the current through a thermoelectric cooler. A 100-Q platinum resistance thermometer is... 

The underline cursor is selectively erased and rewritten each time a character is entered. The laser, which has its heat sink maintained at 10 C by a thermoelectric cooler, emits about 15 mW GW. A pair of f/2 lenses collects and focuses about 3 mW into a 3x15 ym beam at the LC cell. Overlapping spots are written on 10 ym centers over a field of 7 mm diameter. The laser pulse time is 120 ysec which implies an energy of 0.36 yJ per spot. This is... 

The S -band system uses a samarium cobalt permanent magnet, with a fixed field of 1180 G that is swept by a coil over a narrow range of 135 G. This corresponds to a frequency of 3.5 GHz. The system (Figure 3.81) includes an integrated touch screen, internal computer, thermoelectric cooler, and power supply. The instrument is available in an x-band version (9.5 GHz 3480 200 G). 

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