Multi-bed adsorption heat pump cycles and their optimal operation

The chapter consists of two parts. The first part describes advanced adsorption heat pump cycles. The second part presents cycle simulations with optimization to maximize cooling effect. Multi-stage adsorption heat pump cycles are expected to utilize low temperature heat of 50-70 degC. Two-stage cycle and three-stage cycle have been investigated experimentally to clarify appropriate range of heat source temperature. Furthermore, new single stage cycles are proposed based on an idea of reheat scheme, where single stage cycle operates as quasi-two stage cycle. It can expand the temperature range for lower side. The other interesting idea is single stage cycle with three beds in contrast with two beds of conventional single stage cycle. The third bed runs twice as quickly as the other beds to adsorb more vapor from the evaporator. The process of mass recovery from desorption side to adsorption side has an important role in the cycles. Configuration, operation and performance of the cycles are described in the first part. In the second part, adsorption cycles have some control variables for the operation such as cycle time allocation for adsorption, desorption, precooling, preheating processes. It means that cycle has freedom to maximize the performance under given external conditions. It was, however, difficult to attain the optimum due to large freedom of the system. The authors succeeded to employ a nonlinear optimization technique named Particle Swarm Optimization to find optimal time allocation. The method, optimal settings of the parameters and optimal performance are discussed.