Liquid jets cooling

Several instniments have been developed for measuring kinetics at temperatures below that of liquid nitrogen [81]. Liquid helium cooled drift tubes and ion traps have been employed, but this apparatus is of limited use since most gases freeze at temperatures below about 80 K. Molecules can be maintained in the gas phase at low temperatures in a free jet expansion. The CRESU apparatus (acronym for the French translation of reaction kinetics at supersonic conditions) uses a Laval nozzle expansion to obtain temperatures of 8-160 K. The merged ion beam and molecular beam apparatus are described above. These teclmiques have provided important infonnation on reactions pertinent to interstellar-cloud chemistry as well as the temperature dependence of reactions in a regime not otherwise accessible. In particular, infonnation on ion-molecule collision rates as a ftmction of temperature has proven valuable m refining theoretical calculations. 

The temperature of a liquid metal stream discharged from the delivery tube prior to primary breakup can be calculated by integrating the energy equation in time. The cooling rate can be estimated from a cylinder cooling relation for the liquid jet-ligament breakup mechanism (with free-fall atomizers), or from a laminar flat plate boundary layer relation for the liquid film-sheet breakup mechanism (with close-coupled atomizers). 

Installation of agitating nozzles is recommended if sensible liquid heating or cooling is to be used with plain jackets. Nozzles produce liquid jets directing the inlet jacket fluid in a spiral fashion into the jacket. This increases the effective velocity and turbulence level. Vendors have information dealing with their performance and installation. 

Figure 6.35. DTA calorimeter cell described by Barral) et al. (94). A. B. copper sample cups. 4-mra O. D. by 6 mm C,copper reference cup D. two-conductor ceramic supports. 3-mm diameter by 50 mm E. copper radiator shield, 35-mm diameter by 53 mm F, program-sensing thermocouple G. liquid CO cooling gas jet H, electric furnace. 45-mm id by 100 cm 1. copper base plate. 38-mm diameter.

Futrell et al. applied three different techniques to evaporate substances of low volatility in a controlled manner and to cope with the cooling effects that arise when the liquid jet expands on entering the mass spectrometer ... 

Particles, especially shaped particles are known to increase the viscosity of a suspension, following Mooney-Einstein [53]. Thus, carbon particles [12] may enter into the surface or skin of a liquid inviscid jet and increase its viscosity sufficiently and long enough to facilitate its solidification and fiber formation. For this mechanism to be viable, three conditions must be fulfilled. (1) The increase in the jet surface viscosity must afford a stabilized (assisted) jet lifetime that at least matches the jet cooling time. (2) The assisted lifetime resulting from the viscosity increase must be comparable to the actual (unassisted) lifetime of a typical silicate fiber such as E-glass. (3) The surface viscosity increase needed to achieve this lifetime must be realistically achievable by carbon insertion in the jet surface. 

Wang, E.N., Zhang, L., Jiang, L., Koo, J., Goodson, K.E., Keim) T.W., Maveetu, J.G., and Sanchez, E.A., Micromachined jet arrays for liquid impingement cooling of VLSI chips, in Solid-State Sensor, Actuator and Microsystems Workshop,... 

---