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[en] Highlights: • A cross-flow dew point evaporative cooler prototype is investigated. • The performance of a practical evaporative cooling system is tested and analyzed. • A mathematical model is developed for the cross-flow dew point evaporative cooler. • The coupled dehumidification and cooling process is simulated. - Abstract: This paper investigates the cooling potential of a cross-flow dew point evaporative cooler under various conditions. Preliminary study reveals that the dew point evaporative cooler’s performance does not approach its designed capacity when the ambient humidity goes beyond the thermal comfort zone. To address this problem, an air dehumidification process is proposed before the evaporative cooling takes place. It is observed that the cross-flow cooler is able to achieve improved cooling effectiveness when an appropriate inlet air humidity condition is realized. The influence of different dehumidification levels on its cooling capacity and efficiency is subsequently analyzed. Additionally, a mathematical model is developed to predict the cooler performance. Key findings from this study are: (1) The maximum discrepancy between the simulation results and experimental data is within ±3.0%; (2) the overall wet bulb and dew point effectiveness of the cross-flow cooler can reach 1.25 and 0.85 for cooling of the supply air with moderate humidity; (3) the respective wet bulb effectiveness, cooling capacity and COP of the cross-flow system are 0.86, 2.2 kW and 4.6 under humid ambient air condition; and (4) the dehumidification of the supply air enables the cooling capacity and energy efficiency to be improved by 70–135%.
[en] A dual-mode thermochemical sorption energy storage system using working pair of expanded graphite/SrCl2-NH3 was proposed for seasonal solar thermal energy storage. The proposed system has two working modes to produce useful heat with an expected temperature during the discharging phase according to the different ambient temperatures, including the direct heating supply and temperature-lift heating supply. Solar thermal energy is transformed into chemical bonds and stored in summer, and the stored energy is released in the form of chemical reaction heat in winter. The direct heating supply mode is adopted at a relatively high ambient temperature in winter. The effective energy storage density is higher than 700 kJ/kg and the corresponding system COP is 0.41 when the heat output temperature and ambient temperature are 35 °C and 15 °C, respectively. The specific heating power increases with the decrease of heat output temperature for a given ambient temperature. The temperature-lift heating supply mode is adopted to upgrade the heat output temperature at a low ambient temperature below 0 °C in winter. It can produce heat with a temperature above 70 °C although the ambient temperature is as low as −15 °C. It is desirable to further improve the system performance using low mass ratio and high global conversion. Experimental results showed the advanced dual-mode thermochemical sorption energy storage technology is feasible and effective for seasonal solar thermal energy storage. - Graphical abstract: Working temperature range of dual-mode thermochemical sorption energy storage system during the discharging phase in winter. - Highlights: • A dual-mode seasonal solar thermochemical sorption energy storage system is developed. • The sorption working pair is strontium chloride/expanded graphite-ammonia. • Two working modes can be performed according to the different heat requirements in winter. • Energy density and COP of direct heating supply mode are 706 kJ/kg and 0.41 respectively. • Temperature-lift heating supply mode can meet heat demand at low ambient temperature.
[en] Highlights: • A novel self-adaptive sorption system is proposed to reduce nitrogen oxides emission. • Annual required mass of composite sorbents for the novel system ranges from 143 kg to 246 kg. • Annual required volume of composite sorbents is in the range from 358 L to 615 L. • Cost of sorption SCR system by using most composite sorbents is much lower than that of adblue. - Abstract: A novel self-adaptive sorption system is proposed and analyzed, which is considered as an alternative solution to reduce nitrogen oxides emission. Compared with conventional selective catalytic reduction technology, urea solution tank is replaced with sorption reactor for ammonia storage. Composite sorbents are developed with expanded natural graphite treated with sulfuric acid as the matrix. Different sorption working pairs are selected for evaluating working performance of novel system based on testing nitrogen oxides emission of a diesel engine. It is indicated that for operation mode 8, the highest required mass of urea solution per hour could reach 1.9 kg, which is 2.32 times higher than that of composite ammonium chloride. For different composite sorbents, annual required mass ranges from 143 kg to 246 kg and 81 kg to 140 kg in terms of mode 8 and 6 whereas annual required volume is in the range from 358 L to 615 L and 204 L to 350 L, respectively. Cost of novel sorption system by using composite sorbents is generally lower than that of conventional system by using urea solution. It analyzes the feasibility of novel self-adaptive sorption system, which reveals great potential for reducing nitrogen oxides emission.
[en] Highlights: • A promising modular sorption thermal cell is analyzed for combined cold and heat storage. • Permeability of novel composite sorbent is further improved by adding carbon coated nickel. • Sorption rate of novel sorbent is accelerated based on heat and mass transfer enhancement. • Sorption thermal cell of novel composite sorbent has great potentials for scaling applications. - Abstract: Novel composite strontium chloride is developed with expanded natural graphite and carbon coated nickel as the additives. It is indicated that expanded natural graphite and carbon coated nickel are conducive to heat and mass transfer performance, which result in improved sorption characteristic. For composite sorbents with carbon coated nickel, thermal conductivity and permeability range from 0.57 W · m−1 K−1 to 1.93 W m−1 K−1 and from 2.98 × 10−10 m2 to 2.71 × 10−13 m2. Novel composite strontium chloride with carbon coated metal enjoys the faster desorption and sorption reaction rate than that without carbon coated metal. For different evaporation temperatures, sorption quantity of novel composite strontium chloride ranges from 0.28 kg kg−1 to 0.7 kg kg−1. Based on testing results of sorbents with carbon coated nickel, a promising sorption thermal cell is developed and analyzed for combined cold and heat storage, which greatly enhances the versatility and working reliability. Under different working conditions, cold and heat density range from 384 kJ kg−1 to 811 kJ kg−1 and 549 kJ kg−1 to 1648 kJ kg−1. Modular sorption thermal cell could be flexible connected to sorption battery for scaling applications, which reveals great potentials for renewable energy utilization and waste heat recovery.