Thermoelectric Coolers and Assemblies for Medical Applications

Introduction

Medical lasers are designed for use in hospitals, outpatient surgical centers, and physician offices. They combine cutting, ablation, and coagulation properties for precise, virtually bloodless procedures; minimizing thermal damage to the surrounding tissue and increasing recovery time. They also sanitize the area through the heat of the laser, destroying any microbiological bodies that could lead to infection. Although medical lasers are valuable to many medical treatment applications, they do generate waste heat that affects the lasers performance when in operation. They also have size constraints, power consumption requirements, and noise restrictions that make thermal management difficult. 

Thermoelectric Coolers 

Thermoelectric coolers are solid-state heat pumps that require a heat exchanger to dissipate heat via the Peltier effect. During operation, DC current flows through the thermoelectric cooler to create heat transfer and a temperature differential across the ceramic surfaces, causing one side of the thermoelectric cooler to be cold, while the other side is hot. A single-stage thermoelectric cooler can achieve temperature differentials of up to 70°C and transfer heat at a rate of up to 150 watts. In order to increase the amount of heat pumping capacity, the thermoelectric cooler’s modular design allows for the use of multiple thermoelectric coolers mounted side-by-side, which is called a TE array.

Thermoelectric cooler device

Thermoelectric coolers are composed of two ceramic substrates that serve as electrically insulating materials and house P-type and N-type semiconductor elements. Heat is absorbed at the cold junction by electrons as they pass from a low-energy level in the P-type element onto a higher energy level in the N-type element. At the hot junction, energy is expelled to a thermal sink as electrons move from a high-energy element to a lower-energy element. 

Reversing the polarity changes the direction of heat transfer. Thermoelectric coolers are rated at maximum parameters (ΔTmax, Imax, Vmax, and Qmax) under no load conditions, with temperature control accuracy achieving ±0.01°C under steady-state conditions. They can cool to -100°C (6-stage) and pump up to 15 watts per centimeter square of heat, with higher heat pumping capacities achieved by wiring thermoelectric coolers into an array. Their geometry can vary from 2x2 mm to 62x62 mm and are much more efficient in heating mode than resistant heaters. They also fit into tight geometric space constraints and can be mounted in any orientation that cannot accommodate a much larger compressor-based system. 

UltraTEC Series

 

Thermoelectric Cooler Assemblies 

Thermoelectric cooler assemblies are cooling and heating systems that use thermoelectric coolers to transfer heat by air, liquid or conduction methods that include integrated temperature controls. Thermoelectric coolers remove the passive heat load generated by the ambient environment in order to stabilize the temperature of sensitive components used in medical lasers. 

Direct-to-air-Tunnel-Series

Direct-to-air Tunnel Series

Air-to-air Tunnel Series

Air-to-air Tunnel Series

Direct-to-air Powercool Series

Direct-to-air PowerCool Series

 

Thermoelectric coolers are designed and manufactured to strict process control standards and pass/fail criteria, assuring that our customers receive the best possible thermoelectric coolers. Our standard product portfolio includes an extensive array of thermal management solutions that cover a wide range of cooling capacities with compact form factors and high coefficient of performance. The standard product offering includes heat transfer mechanisms designed to absorb and dissipate heat by convection, conduction or through liquid heat exchangers. All products are manufactured in an ISO 9001:2008 certified facility. 

Since there are so many attributes that need to be ascertained for each application, often a customized thermoelectric cooler assembly will yield a more optimal thermal solution. Laird Thermal Systems offers strong engineering services with a global presence that supports onsite concept generation, thermal modeling, thermal design and rapid prototyping. We also offer validation test services to meet unique compliance standards.

Conclusion

Thermoelectrics provide good temperature stabilization to maintain peak performance of a medical laser and offer solid-state operation, low maintenance, and long service life. Thermoelectrics also make an excellent thermal management solution due to compact size no vibration and low total cost of ownership. This cannot be accomplished by any other means without a complex heating and cooling system.

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Applications
Medical
Medical Lasers

Product Section
Thermoelectric Modules