| Along with the society's steady pace of development and advancement,China's industrial energy cost rises every year.Especially the heating energy used in the Northern part of China takes up a significant amount of percentage in energy cost.At the same time,the Northern part of China possesses coal and gas as a way of producing heat.This way of using energy also brings a lot of environmental pollution which evoke concerns among the society.Under the double pressure of heating demand and environmental pollution,it is essential to develop energy-saving and environment-friendly heating methods.Condensation of direct condensate radiant floor heating system with air source heat pump is appreciated for the advantages of high efficiency and environmental protection.However,since the system has been introduced into China for a short time,it is still immature with imperfect technology and standards.It is a new radiant floor heating system.This paper analyzes the selection of refrigerant,the influencing factors of heating effect,the optimal length of the ground pipes and the condensation heat transfer in the pipe to make an intensive study on this system.The main work is as follows:(1)In this paper,the five refrigerants R410 A,R407C,R22,R32 and R134 a are comprehensively analyzed and compared from basic physical parameters of refrigerants,the coefficients of theoretical cycle performance,systemic pressure,the coefficients of condensation heat transfer and the discharge capacity of air compressor,and R410 A the most suitable refrigerant for this system.R410 A is non-toxic and nonflammable,which will not damage the ozonosphere or cause greenhouse effect.Its thermodynamic and physical properties are similar to azeotropic refrigerants.It is suitable for the air source heat pump system in low temperature for its good heat performance and small size of equipment required.(2)This paper simulates different temperature of heat medium,designed temperature indoor,pipe spacing,pipe diameter and surface material with FLUENT to obtain the corresponding heat flow density on the upper and lower surfaces of the floor and the surface temperature of the floor,which are made into tables for reference in practical engineering.To compare the five elements' disturbance to the heat flux;According to the relative heat flux density rate,we can state that the heat source's disturbance is at its highest state when rising from the floor.We also learned that the diameter of the tubes has the least amount of influence toward the heat flux density.Furthermore,the heat source's disturbance is also at its highest state when descending from the floor,and the covering materials also has the least influence toward the heat flux density.On the basis of satisfying indoor heat load,it is the most comfortable and energy-saving with the heating medium temperature of the system is at 35?40?,and the pipe spacing is at 150?200mm.(3)To enhance the system's ability to exchange heat,we experimented with the measurements of 5.7m×3.9m×3.3m for the room.Through the simulation,we used a cooling chemical to perform steam liquefaction inside the tubing.At last,we found out that the best length for the tubing layout is 21.3m.Different mass flow rate,pipe diameter and condensation temperature of the refrigerant are set up in this paper to analyze their influence on the condensation heat transfer capacity of the refrigerant.Provided that other conditions are invariant,the condensation temperature is lower when the mass flow rate is larger,the condensate film in the ground pipe is thinner when the pipe diameter is smaller,the condensation heat transfer coefficient is larger and the heat transfer effect is more obvious when the thermal resistance is smaller. |
PDF Full Text Request