| The continuous advancement in building energy conservation efforts in China has significantly reduced the heating load of buildings.China has begun to adopt low-temperature continuous heating methods,reflecting a gradual reduction in the temperature of the heating medium.The increasing promotion of renewable energy heating technology and district heating in southern regions has encouraged a greater reliance on low-temperature heat sources for building heating.Studying the scientific challenges of improving the thermal performance of radiators under low-temperature conditions and evaluating the effectiveness of low-temperature heating can guide designers in selecting and using radiators effectively,thereby optimizing the final heating effect.Furthermore,it can promote the development of low-temperature heating technology,particularly those powered by renewable energy,and drive the upgrading of equipment in the low-temperature radiator industry.This thesis employs a combined approach of experimentation and computer simulation to conduct a comprehensive study on radiator design selection,thermal performance optimization,heating effect evaluation,and application prospects under low water supply temperature conditions.To quantify the heat dissipation attenuation of radiators under low-temperature water supply conditions,this paper uses experimental methods to investigate the heat dissipation characteristics of eight types of radiators commonly used in China.Regression and mathematical statistical techniques are applied to categorize and organize the experimental results.This article presents correction coefficients for radiating,natural convection,and forced convection radiators across various excess temperature ranges,updating the calculation methods for radiator quantities in relevant standards.These findings have enriched and refined the technical requirements for low-temperature heating with radiators in HVAC standards.Employing computational fluid dynamics(CFD)simulation and experimental verification,this thesis explores optimal techniques to enhance the thermal performance of radiators in low-temperature conditions.The study explores two improvement avenues: optimizing product structural parameters and incorporating forced convection measures.Research demonstrates that incorporating vortex generators and staggered fins in panel radiators can increase heat dissipation efficiency by 5% to 7% without significantly altering the heat dissipation area.By optimizing the heat dissipation structure with discontinuous fins,the overall heat dissipation of the radiator can be reduced by less than 5%,while the material usage for fins can be decreased by 42% when the fin gap is less than 0.03 m,thereby reducing manufacturing costs.This article also investigates the compensatory capacity of enhancing convective intensity to mitigate the impact of reduced supply water temperature and presents a compensatory design algorithm through data regression.These findings provide valuable guidance for product improvement and conversion under low-temperature heating conditions.To evaluate the operational characteristics and heating effectiveness of forced convection radiators,this thesis utilizes a 57-node human body thermophysiological model that integrates metabolic factors with heating environmental variables.Using this model,the local thermal comfort of the human body is evaluated and the feasibility of forced convection radiator heating is demonstrated through a comparison with radiant floor heating.The study reveals that the air supply speed of the radiator influences thermal comfort,with skin temperature peaking at approximately 3 m/s airspeed.As the air velocity increases,thermal comfort decreases.Due to clothing’s thermal resistance,the use of top-air supply and side-bottom air supply modes has minimal impact on local thermal comfort indicators for the body trunk,limbs,and feet.When the air supply speed exceeds 2m/s,indoor air stratification is reduced,enabling both air supply modes to achieve similar thermal comfort targets.Compared to floor radiation heating under similar indoor temperature conditions,these two techniques exhibit comparable thermal comfort effects.This article introduces a method to directly quantify the heating effect of heating equipment by calculating human thermal physiological parameters in the heating environment.To assess the suitability of low-temperature heating technology with radiators in severely cold and cold regions of China,this thesis establishes an analysis model using the TRNSYS platform.Employing scenario analysis,it evaluates the low-temperature heating performance of radiators under various scenarios created by combinations of different envelope structures and water supply temperatures,considering indoor temperature and Predicted Mean Vote(PMV)indicators.The findings indicate that the reduction in heat dissipation resulting from decreased water supply temperature is largely consistent with the reduction in heating load achieved through envelope performance improvements.Consequently,indoor thermal comfort remains unaffected under this synergistic effect.A comparative analysis is conducted on the comfort and economy of low-temperature heating with radiators versus floor radiation heating.The results indicate that low-temperature heating with radiators can achieve a similar thermal comfort level to floor radiation heating after adjusting the number of radiators but with lower costs and higher cost-effectiveness.This study comprehensively addresses the key technologies involved in the entire process of low-temperature heating with radiators.Based on theoretical analysis and experimental research,it establishes a comprehensive technical system that includes experimental testing,performance simulation,effect evaluation,and technical application.This framework provides technical support for the improvement,optimization,and effect evaluation of low-temperature radiator heating technology,and is of great theoretical and practical value. |
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