Ta Instruments-waters LLC

Mark Heyman

John W Schaefer

A liquid nitrogen cooling assembly incorporating a liquid detector which feeds back to control the nitrogen supply is disclosed. A pressure-controlled nitrogen source (e.g., a dewar) feeds liquid nitrogen to a heat exchanger mounted to a differential scanning calorimetry (DSC) cell. The DSC cell is cooled as liquid nitrogen in the heat exchanger contacting the cell is vaporized into nitrogen gas. The exhaust (nitrogen gas and, occasionally, nitrogen liquid) is fed to a liquid detection/evaporator assembly. If liquid nitrogen is detected in the exhaust by the liquid detection/evaporator assembly, an indication is fed back using a liquid detection feedback loop to a pressure control device. The pressure control device reduces the amount of pressure on the nitrogen source in order to eliminate liquid in the exhaust. When there is liquid in the exhaust, the liquid detection/evaporator assembly also collects and vaporizes the exhaust liquid so that it can be properly vented to atmosphere in gas form. When liquid is no longer detected in the exhaust, the pressure control device increases the pressure on the liquid nitrogen source until liquid is detected in the exhaust. Subsequent cycles control pressure in this manner to keep the heat exchanger full of liquid nitrogen.

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Mays Landing, NJ, United States of America

Mark Heyman