This paper presents experimental and theoretical studies of a new compact calorimetric cell under laboratory conditions. Producing a reduced-size calorimetric cell, intended to be used to quantify the nuclear heating rate inside material testing reactors by differential calorimetry, is a major challenge and offers new complementary measurement prospects. The new compact design, called CALOrimeter with radial thermal transfers for nuclear REactors, is obtained with a special geometry favoring heat transfers in the radial direction in order to decrease the height of the sensor. Results obtained during a crucial preliminary step corresponding to out-of-pile calibration without nuclear rays are presented and compared with those of three different configurations. The influence of different parameters, such as a specific area of the cell structure, fluid temperature and velocity, and the nature of the material of the cell structure, is shown and analyzed with a 1-D thermal model coupling conductive and radiative thermal exchanges. Comparisons of different configurations and conditions lead to a discussion of the advantages of this new compact design.