This week I finally performed the measurement of the condensation rate of GAr in a tube heat exchanger immersed in LAr at various differential pressures. This test helps us to dimension the size and define the geometry of the heat exchanger for DS-20k, needed to boil of energy-efficiently 1000 slpm for recirculation. I measured the heat transfer coefficient for LAr-GAr cooling and phase change, and for LAr-LAr cooling.