Design of a high-pressure circulating pump for viscous liquids
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Design of a high-pressure circulating pump for viscous liquids 

The design of a reciprocating dual action piston pump capable of circulating viscous fluids at pressures of up to 34 MPa _5000 psi_ and temperatures up to 80 °C is described. The piston of this pump is driven by a pair of solenoids energized alternatively by a 12 V direct current power supply controlled by an electronic controller facilitating continuously adjustable flow rates. The body of this seal-less pump is constructed using off-the-shelf parts eliminating the need for custom made parts. Both the electronic controller and the pump can be assembled relatively easily. Pump performance has been evaluated at room temperature _22 °C_ and atmospheric pressure using liquids with low and moderately high viscosities, such as ethanol and corn oil, respectively. At ambient conditions, the pump delivered continuous flow of ethanol and corn oil at a flow rate of up to 170 and 17 cm3 /min, respectively. For pumping viscous fluids comparable to corn oil, an optimum reciprocation frequency was ascertained to maximize flow rate. For low viscosity liquids such as ethanol, a linear relationship between the flow rate and reciprocation frequency was determined up to the maximum reciprocation frequency of the pump. Since its fabrication, the pump has been used in our laboratory for circulating triglycerides in contact with supercritical carbon dioxide at pressures of up to 25 MPa _3600 psi_ and temperatures up to 70 °C on a daily basis for a total of more than 1500 h of operation functioning trouble free.
I. INTRODUCTION
In phase equilibria studies, one can significantly shorten the time needed for equilibration by using a circulating pump. Seal-less magnetically coupled pumps offer the advantage of avoiding the use of elastomeric seals or lubricants, thereby minimizing the occurrence of leaks, downtime, and the need for maintenance. Furthermore, with a seal-less magnetically coupled pump all wetted parts can be made of stainless steel, which is particularly attractive for applications where the fluid is under high pressure, toxic, or corrosive. A review of the scientific literature reveals numerous innovative designs for magnetically coupled pumps, with the majority of the published work describing reciprocating positive displacement pumps. Commercially available magnetically coupled pumps are often centrifugal or gear pumps _HMD/Kontro, Micro pump_ rated up to about 34 MPa _5000 psi_, wh