Dissipative Heat Generation and Optimization of Operating Conditions in Cryogenic Grinding of Waste Rubber

To address the influence of dissipative heat generation on operating-condition selection during the low-temperature grinding of waste rubber under vapor-compression refrigeration, a discrete element method （DEM） model of a vibrating cryogenic crusher was established, with the glassy-state mechanical parameters of rubber calibrated by cryogenic uniaxial tensile tests. Normal heat power （P_n） and tangential heat power （P_t） were proposed to characterize the dissipative heat generation behavior during the grinding process. Based on this model, an L₂₅（5⁶） orthogonal design was employed to systematically investigate the effects of rotational speed, feed particle size, and filling ratio on the dissipation behavior. Range analysis, analysis of variance （ANOVA）, quadratic response surface regression, and Pareto-front analysis were further combined to identify the dominant factors, interaction effects, and dual-objective matching relationship of process parameters. The results showed that the range effects of the three factors on both P_n and P_t followed the order of rotational speed, feed particle size, and filling ratio. Rotational speed was the only factor with a significant main effect on both responses （p<0.001）; the corresponding ranges in normal and tangential heat power were 239.31 W

and 164.65 W, respectively. Both P_n and P_t increased markedly with rotational speed, whereas the overall main effects of feed particle size and filling ratio across their five levels were not significant at the 0.05 level. The response surface results showed that high P_n values occurred mainly at high rotational speeds, while the rapid increase in P_t occurred when high rotational speed was combined with small feed particle size. Pareto analysis further revealed a clear trade-off between strengthening normal action and controlling tangential dissipation. Within the investigated parameter range, rotational speed is the main factor affecting contact dissipation, and operating conditions should balance normal action with tangential heat generation. These findings provide a reference for parameter matching in cryogenic grinding under vapor-compression refrigeration.