Experimental Studies Towards Development of a Single Stage High Refrigerating Capacity G-M Type Pulse Tube Refrigerator

Abstract

The absence of moving components at low temperature end gives the pulse tube refrigerator(PTR)a great leverage over other cryocoolers like Stirling and G-M refrigerators that are conventionally in use for several decades.PTR has greater reliability;no electric motors to cause electromagnetic interference,no sources of mechanical vibration in the cold head and no clearance seal between piston and cylinder.Moreover,it is a relatively low cost device with a simple yet compact design.The objectives of the present work is to design,fabricate and test a single stage G-M type pulse tube refrigerator and study its performances.Experimental studies consists of cooling behavior of the refrigeration system at different cold end temperatures and optimization of orifice and double inlet openings at different pressures.The developed pulse tube refrigerator consists of compressor,rotary valve, regenerator,pulse tube,hot end heat exchanger,orifice valve and double inlet valve,reservoir or buffer,vacuum chamber and coupling accessories etc.Regenerator and pulse tube have been chosen according to the literature available.Hot end heat exchanger has been designed and fabricated with respect to the regenerator and pulse tube geometry.The assembly of the components has been done in such a way that the set-up can be used as basic pulse tube refrigerator,orifice pulse tube refrigerator or double inlet pulse tube refrigerator as and when required.This has enabled thorough comparison among them.The effect of operating conditions such as average pressure and pressure ratio of the compressor also has been found out.The optimum operating conditions such as opening of the orifice and double inlet valves have been selected according to the performance i.e. minimum attainable temperature at no load condition.Effect of orifice and double inlet openings at different pressures has been detected by applying the pressure sensors across at various positions in the system.Correspondingly,pressure variations at regenerator inlet,pulse tube and reservoir has been determined.