Specific heat capacities and flow resistance of an activated carbon with adsorbed helium as a regenerator material in refrigerators

An ideal regenerator material is characterized by a high specific heat capacity and a low flow resistance, and the specific heat capacity of the working gas must be low. However, the specific heat capacity of a helium working gas is much higher than that of the general regenerator materials in the temperature range 4-30 K, which severely limits the improvement of the refrigerator performance. The helium adsorption capacity of the activated carbon was first evaluated. The heat capacity and flow resistance of the activated carbon with adsorbed helium were measured and compared with the commonly-used regenerator materials such as stainless steel wire mesh, lead, and magnetic Er3Ni and HoCu2. Results show that the specific heat capacity of the activated carbon with adsorbed helium are higher than those of the other materials investigated at 3.0 MPa and 16-25 K, and its flow resistance is close to that of Er3Ni, a little bit higher than that of HoCu2, and much less than that of the stainless steel wire mesh. These results confirm that it is feasible to use activated carbon with adsorbed helium as a regenerator material.