Performance Study And Optimization Of Silica Gel-water Adsorption Refrigeration System Using Modular Adsorber

Silica gel-water adsorption refrigeration is green and energy-saving, which makes it a ideal refrigeration technology. The research purpose of silica gel-water adsorption refrigeration is the improvement of market development and commercialization via improving system efficiency and reliability, reducing system size, reducing system cost, etc.Main work of this paper is performance study and optimization of silica gel-water adsorption refrigeration system using modular adsorber. As a result, this paper focuses on heat exchanger network optimization of adsorption refrigeration system, study of different heat recovery methods, system simulation, modular design, manufacture and test of silica gel-water adsorption chiller. The main research can be described as follows:(1) A method of heat exchanger network optimization of adsorption refrigeration is built on pinch point technology. According to the stable feature of pinch point technology, T-H diagram and question table of adsorption refrigeration are built without considering the time factor. Then, the results are analyzed with considering the time factor. Through the pinch point analysis on a two-adsorber system, pinch point is located in the top of hot fluid curve and the main heat recovery is between desorption and adsorption curves. After the heat exchanger network is optimized, ideal COP of the two-adsorber system can reach 3.48. Besides, the ideal COP of optimized two-evaporator and two-stage systems can be 3.07 and 0.85, respectively. When the time factor is considered, the ideal COP of optimized two-adsorber and two-evaporator systems reduces to 1.20 and 1.13, which are worse than those cases without considering the time factor. To eliminate the effect of time factor, the adsorber has to be fluidized. That means a modular adsorber is needed.(2) By researching the schematic of three different heat recovery methods, advantages and disadvantages of them can be showed and serial and passive heat recovery methods are preliminarily selected because of their outstanding advantages. And then, a simple adsorber is selected as a research object and mathematical models of different heat recovery methods are built. Simulation is done and the results are obtained. Optimal heat recovery time estimates the ratio of tube length and fluid rate. Passive heat recovery method has a effective heat recovery time range, which makes it less reliable than the serial heat recovery method.(3) A silica gel-water adsorption chiller using serial heat recovery and mass recovery-like processes and modular adsorber is designed. At first, effective thermal conductivity of silica gel is measured for system design. A modular adsorber is designed, which can meet the requirement of standardizing and massive production. Also, the modular adsorber has a good performance in heat and mass transfer. The system structure of this silica gel-water adsorption chiller is two-chamber type, which is conducive to improvement of system reliability. For the further system performance improvement, the evaporator in this chiller is designed with capillarity-auxiliary enhanced heat transfer technology.(4) Simulation of silica gel-water adsorption chiller using modular adsorber is done. Three-part heat exchange model of dividing wall type heat exchanger is employed in the modeling of adsober, condenser and evaporator. The modeling of reservoir is also done in this simulation. Those modeling equations are solved by the calculation method which can avoid the effect of parameter initialization. Under the typical conditions(85 oC hot water, 30 oC cooling water and 10 oC chilled water), cooling capacity, COP and SCP are 51 kW, 0.53 and 149 W·kg-1, which meets the design requirements.(5) A silica gel-water adsorption chiller using modular is bulit. Besides, its testing system is also bulit and it has been tested. The system design and simulation can be verified by the test results. The running characteristic, optimal cooling time, optimal mass recovery-like time, optimal heat recovery time and system peformance under different conditions can be obtained via the test results. Under the typical conditions(85.5 oC hot water, 29.5 oC cooling water and 11.1 oC chilled water), cooling capacity, COP and SCP are 42.8 kW, 0.51 and 125.0 W·kg-1, respectively. When the outlet temperature of chilled water increases to 14.7 oC, cooling capacity, COP and SCP increase to 52.0 kW, 0.65 and 146.4 W·kg-1, respectively.Through performance study and optimization of silica gel-water adsorption refrigeration system using modular adsorber, this paper can offer valuable experience in theory, design and test, which is conductive to the application of silica gel-water adsorption refrigeration.