In this article, the working fluid to be placed in the Heat Pipes of a selected Heat Pipe Air Recuperator and the filling amount of this fluid will be determined by calculation. In the heat pipe air recuperator selected for calculations, there are a total of 18 heat pipes to be filled with working fluid. The amount of working fluid to be filled into each heat pipe is determined by calculation, and the inside of the pipes are put under vacuum before filling and the air inside them is taken out. Afterwards, fluid filling is performed. Since "water" is selected as the working fluid for the heat pipe, the calculated amount of demineralized boiler feed water will be used in the filling process. Wick materials made of stainless steel and having two different pore numbers (meshes) are placed in the pipes. Since both types of wicks were placed in the pipes in two layers, a total of 4-layer wick structure was obtained, with 120 mesh wicks in 2 layers and 200 mesh wicks in 2 layers, thus placing them in the pipes of the recuperator. [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [37].