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Based on the concept of a diffusion absorption system,a hot-cold conversion pipe utilizing 1,1,1,2-tetrafluoroethane (R134a)-dimethylformamide (DMF)-helium (He) as the working pair is presented with the aim of cooling output by recovering the low-grade waste heat.The model of the hot-cold conversion pipe is established,in which a heat pipe is used to transfer the waste heat as the heat input.The equations of the thermodynamic properties of the working pair are established by equation of state method (EOS).The model of the hot-cold conversion pipe is built based on the mass,species and energy balance equations of each component.The direct conversion of heat to cold is achieved by the desorption,absorption,condensation and diffusion evaporation processes of R134a.The hot-cold conversion pipe is cooled by natural convection,which can be enhanced by chimney effect.The thermodynamic analysis is carried out to analyze the effect of the boundary conditions,i.e.the heat source temperature,the refrigeration temperature,and the environmental temperature,on the system performance.This paper provides a theoretical basis for actual application of the hot-cold conversion pipe in waste heat recovery field.