[b]0 Introduction[/b] Adsorption refrigeration effectively utilizes low-grade energy sources such as solar energy and industrial waste heat without causing environmental damage, and this new refrigeration technology is receiving increasing attention. Adsorption refrigeration does not use Freon as a refrigerant, making it an environmentally friendly refrigeration technology. Adsorption refrigeration systems can be directly driven by low-grade energy sources such as solar energy and industrial waste heat, making them an effective tool for energy conservation and the development and utilization of new energy sources such as solar energy. This system has advantages such as simple structure, no moving parts, no noise, good vibration resistance, and long service life, and has considerable application prospects in marine refrigeration, automotive refrigeration, and aerospace refrigeration. For example, using it in an air conditioning system driven by engine exhaust can meet the refrigeration needs of vehicles [1, 2]. In various buses and cars, adsorption refrigeration refrigerators can continue to refrigerate for more than 12 hours after parking. Taking the Jiefang CA15 freight truck as an example, when operating under a partial load of 60kW, the usable exhaust heat is about 18.28kW. With a COP of 0.2 to 0.3 (which current adsorption refrigeration systems can fully achieve), the generated cooling capacity is 3.66 to 5.48kW, while the required cooling capacity in the cab is generally about 3.5kW. It can be seen that the generated cooling capacity can meet the demand. If the adsorption refrigeration technology that utilizes waste heat can be successfully applied to various engine air conditioning and refrigerator systems, and a high-performance, low-cost, small-sized engine exhaust waste heat utilization adsorption refrigeration system with virtually no operating costs can be successfully developed, it will bring huge economic and social benefits. Analysis of the efficiency and thermal balance of automobile engines shows [3, 4] that only 30% to 48% of the total heat from fuel combustion is used for the power output of the automobile (see Table 1), and more than half of the heat is discharged outside the vehicle as waste heat, including the heat carried away by the circulating cooling water and the heat carried away by the exhaust gas. The proportion of heat carried away by exhaust gases accounts for 25%–45% of the total combustion heat for diesel engines and 30%–40% for gasoline engines. The temperature at the exhaust valve is 400–600℃. Considering the dew point corrosion problem of acidic oxides in the exhaust gas, the final exhaust gas temperature should not be lower than 180℃. Generally, 15%–20% of the total combustion heat can be utilized, making the usable exhaust waste heat considerable. As the above analysis shows, engine exhaust gases have a high temperature and a large amount of waste heat, making them an ideal driving heat source for adsorption refrigeration systems. If the engine is used directly for adsorption refrigeration experiments, only about 30% of the engine exhaust heat can be utilized, while the remaining 70% of the energy is wasted. Furthermore, the flow rate and temperature provided by the engine remain essentially constant, significantly limiting the research. Therefore, we consider establishing a test bench that can simulate multiple heat sources, with the output heat generated by fuel combustion. This bench can be used to study different engine heat sources and the impact of engine performance under different operating conditions on the adsorption generator. [b]1 Introduction to the Multi-Engine Exhaust Gas Heat Source Adsorption Cooling Simulation Test Bench System[/b] The multi-engine exhaust gas heat source adsorption cooling test bench (see Figure 1) has the following characteristics: (1) It adopts a two-stage air supply system, with the burner fan inlet duct connected to the main fan outlet, avoiding the burner fan directly drawing air from the atmosphere, which would lead to carbon buildup inside the burner and incomplete combustion, affecting the normal operation of the entire test bench. (2) The main fan provides the primary and secondary air required for combustion to the burner, while also providing a large amount of cold air to ensure that the exhaust temperature of the test bench is within a controllable range. (3) A circular afterburner pipe with the same inner diameter as the combustion chamber is used at the burner outlet, which helps to form a jet. (4) The cooling air is drawn by the burner outlet jet to increase the outlet pressure of the combustion flue gas and compensate for the insufficient air pressure of the main fan. (5) The following measures were adopted to adjust the parameters of the flue gas output from the test bench: an adjustable damper was added at the inlet of the main fan; the speed of the main fan was adjusted using a frequency converter; and the fuel quantity of the test bench was adjusted by adjusting the pressure of the burner fuel pump. (6) Two sets of generators were used to alternately refrigerate, so that the system could achieve a continuous cooling effect. [b]2 Debugging of the Test Bench[/b] The parameters (flow rate, temperature, pressure) of the flue gas output from this test bench are adjustable, that is, the simulated heat source can be changed. The air volume and fuel quantity determine the outlet temperature of the flue gas and the simulated heat flow rate of the test bench, and the temperature and flow rate of the flue gas affect the outlet pressure. By adjusting the damper opening, changing the speed of the main fan and adjusting the fuel quantity of the burner, the parameters of the flue gas output from the test bench, such as temperature, pressure and mass flow rate, can be adjusted. Before starting the machine, the atmospheric pressure, temperature, humidity and other parameters were measured. The main fan was started and the sealing of the entire system was checked; the frequency of the frequency converter or the damper opening was adjusted so that the pressure at the inlet flow meter reached the required value. Then, start the burner fan, turn on the burner fuel pump, and start the electric ignition to generate heat from fuel combustion. Adjust the pressure in the fuel supply pipe to meet the fuel quantity requirements. As the outlet pressure increases, the pressure difference at the flow meter will decrease, requiring readjustment of the inverter frequency and damper opening to bring the flow rate to the set value. When the input flow rate and temperature are constant, the outlet flue gas pressure of the test bench remains basically unchanged. [b]3 Test Bench Parameter Calculation[/b] In the simulation test bench, the main parameters to be simulated are the temperature and mass flow rate of the heat source. The amount of fuel consumed by the test bench directly determines the output heat of the flue gas, and it is also an important parameter determining the output temperature. Since there is pressure loss in the generator, the output pressure is also an important parameter in the design of the simulation test bench, which is mainly related to the structure of the generator. The four design parameters in the design of the simulated engine exhaust heat source adsorption refrigeration test bench are: temperature t, mass flow rate Qm, fuel quantity Qb, and pressure P. The engine exhaust gas flow rate is: Qm = Nege (L0αj + 1) Where: Ne—engine shaft power; ge—fuel consumption ratio under rated engine conditions; L0—theoretical air volume required to burn 1 kg of fuel; α—excess air coefficient; j—scavenging coefficient. The heat contained in the exhaust gas is: Q = QmCp (t - t0) Where: Cp—specific heat at constant pressure of the exhaust gas; t—exhaust temperature; t0—ambient temperature, taken as 20℃. The parameters of this simulation test bench during normal operation are: flue gas flow rate 100～1500 m3/h; outlet flue gas temperature 180～600℃; fuel consumption 2～20 kg/h; outlet flue gas pressure 1200～2000 Pa. The heat source of the test bench is provided by the main fan and burner. The outlet flue gas heat flow rate is changed by adjusting the fan speed, damper opening, and fuel quantity. The flue gas flow rate is measured using the throttling and pressure reduction method, and the temperature is measured using a temperature sensor. [b]4 Experimental Results[/b] Experiments were conducted simulating the exhaust gas heat sources of three engines of the same model to investigate the influence of different heat sources on the desorption of the adsorption bed. The performance of the three heat sources is shown in Table 2, and the changes in the ammonia desorption rate of the three heat sources for the same adsorption bed are shown in Figure 2. It can be seen that, due to its low temperature and small flow rate, heat source 1 has a slower heat exchange with the adsorption bed, resulting in the peak ammonia desorption rate of the adsorption bed occurring between 8 and 21 min, with the highest peak at 14 min; after heat source 2 heats the adsorption bed, the peak ammonia desorption rate of the adsorption bed occurs between 4 and 18 min, with the highest peak at 8 min; after heat source 3 heats the adsorption bed, the peak ammonia desorption rate of the adsorption bed occurs between 2 and 16 min, with the highest peak at 8 min. Since the amount of ammonia desorbed by the adsorption bed decreases significantly after the peak desorption period, continuing to heat the adsorption bed would not yield an economical amount of ammonia. Therefore, in the matching of heat sources and adsorption beds, different optimal heating times exist between adsorption beds for different heat sources, and the two sets of adsorption beds achieve continuous cooling through alternating heating. The optimal heating time of the adsorption bed is related to the properties of the heat source, the temperature of the heat source, the flow rate of the heat source, and the structure of the adsorption bed. Finding the optimal heating time of the adsorption bed is closely related to the economy and refrigeration efficiency of the entire adsorption refrigeration system. [b]5 Conclusion[/b] To meet the needs of adsorption refrigeration experiments, an adsorption refrigeration test bench simulating the exhaust gas heat source during the actual operation of an engine was designed. This test bench can simulate the exhaust gas of various engine models within a relatively large adjustment range, which can greatly reduce research costs and shorten the research cycle, providing a certain theoretical and experimental basis for designing adsorption generators under given heat source conditions, and laying the foundation for future experimental research on adsorption refrigeration systems. [b]References[/b] [1] Jiang Zhoushu, Wang Ruzhu, Xu Yuxiong, et al. Performance simulation of adsorption air conditioner in the driver's cab of internal combustion locomotive [J]. Journal of Shanghai Jiaotong University, 2002, 36(2): 176-179. [2] WHOLE Ren Xianzong, Li Aiping. Application of heat recovery from internal combustion engine exhaust gas in bus heating [J]. Agricultural Mechanization Research, 2001, (2): 121-122.  [3] Wei Chunyuan, Zhang Weizheng, Ge Yunshan. Advanced Internal Combustion Engine [M]. Beijing: Beijing Institute of Technology Press, 2001.  [4] Wang Jiankun. Diesel Engine Principles [M]. Shanghai: Shanghai Jiaotong University Press, 1990.  [5] Cerkvenik B, Poredo A, Ziegler F. Influence of adsorption cycle limitations on the system performance [J]. International Journal of Refrigeration, 2001, 24 (6): 475-485.  [6] Zquierdo M, Martin E. The engine exhaust gases as energy source of an air condensed mobile absorption machine [A]. 19th International conference of refrigeration [C]. Proceedings Volume 3a, 1995. [7] Zhao Jianxun, Li Hui, Wang Ruijun, et al. Experimental study on enhanced heat transfer in adsorption bed of chemical adsorption refrigeration system [J]. Energy Engineering, 2002, (1): 43-45. [8] Li Hui, Wan Xiaoli, Zhao Jianxun. Experimental study on thermal conductivity of adsorbent in thermal adsorption refrigeration [J]. Journal of Beijing Institute of Technology, 2003, (1): 38-41.