Study on Heat Transfer Capacity of the Solar Horizontal Heat Pipe

AbstractIn order to study the heat transfer performance of solar horizontal heat pipes, a high-precision experimental apparatus for heat transfer capacity of the solar horizontal heat pipe was developed. It was proved that the system heat balance of the experimental apparatus is less than 10% and the relative error ofthe heat transfer capacity was less than 6%. By heat transfer capacity test, it was shown that when the liquid level height of working fluidwas about 19% ∼ 22% of the inner diameter of solar horizontal heat pipes, the optimal heat transfer performance was obtained.In addition, the heat transfer performance of solar horizontal heat pipes was affected adversely by the installation angle

Evaluation of the Radar QPE and Rain Gauge Data Merging Methods in Northern China

Radar-rain gauge merging methods have been widely used to produce high-quality precipitation with fine spatial resolution by combing the advantages of the rain gauge observation and the radar quantitative precipitation estimation (QPE). Different merging methods imply a specific choice on the treatment of radar and rain gauge data. In order to improve their applicability, significant studies have focused on evaluating the performances of the merging methods. In this study, a categorization of the radar-rain gauge merging methods was proposed as: (1) Radar bias adjustment category, (2) radar-rain gauge integration category, and (3) rain gauge interpolation category for a total of six commonly used merging methods, i.e., mean field bias (MFB), regression inverse distance weighting (RIDW), collocated co-kriging (CCok), fast Bayesian regression kriging (FBRK), regression kriging (RK), and kriging with external drift (KED). Eight different storm events were chosen from semi-humid and semi-arid areas of Northern China to test the performance of the six methods. Based on the leave-one-out cross validation (LOOCV), conclusions were obtained that the integration category always performs the best, the bias adjustment category performs the worst, and the interpolation category ranks between them. The quality of the merging products can be a function of the merging method that is affected by both the quality of radar QPE and the ability of the rain gauge to capture small-scale rainfall features. In order to further evaluate the applicability of the merging products, they were then used as the input to a rainfall-runoff model, the Hybrid-Hebei model, for flood forecasting. It is revealed that a higher quality of the merging products indicates a better agreement between the observed and the simulated runoff

Dual-objective optimization of large-scale solar heating systems integrated with water-to-water heat pumps for improved techno-economic performance

Water-to-water (WWHP) heat pump has been proved highly effective in improving the thermal performance of concentrated solar district heating system (CSDHS). The holistic design method is important to realize the optimal matching and techno-economic performance for CSDHS combined with WWHP. However, such holistic designs are still lacking and thus this study proposes a dual-objective optimization model adopting NSGA-Ⅱ to bridge the research gap. A real CSDHS in Nagarze County, China was used as a case study to validate the proposed model. Solar fraction (SF), heat collection efficiency (HCE) and levelized cost of heat (LCOH) were used as the key indicators to further evaluate the performance of the optimized system. The results showed that compared with the existing system, the performance of the optimized system is significantly improved. With the heating area of 200000m2, the SF and LCOH can be improved from 53.26% and 0.2750 CNY/kWh to 74.17% and 0.2297 CNY/kWh, respectively. Meanwhile, as AHS, the boiler is found inferior to the air source heat pump (ASHP) in the economic performance, but it has larger HSU volume and WWHP capacity. Associated maximum increments of SF and HCE can reach 16.2% and 4.4% respectively. The in-depth study shows that WWHP can constantly improve the thermal performance of the system, but it only improves the system economic performance in the periods with low AHS efficiency or high energy price. The study provides a novel design method which can help improve the techno-economic performance of large scale and complex CSDHS