Designing the Main Heat-Transfer Equipment of an ORC-System for the Internal Combustion Engines of Shipboard Installations

The application of an electricity-generation technology involving the use, in a so-called organic Rankine cycle (ORC), of low-boiling working fluids holds promise for many fields of science and engineering in Russia. Many industrial and technological processes and operation of mechanisms and devices are often accompanied by releasing a large amount of low-grade (rejection) heat. As a rule, this heat is not usefully utilized and dissipates in the environment. Recovering the heat of exhaust gases from gas-turbine engines and diesel-generators in motor-road, railway, marine, and river transport; in gas transportation systems; in military engineering; etc. is one of the most promising application fields of this technology. In particular, an analysis of the technological parameters characterizing the operation of modern shipboard installations makes it possible to judge about the applicability of the ORC technology for improving their energy efficiency. However, the need to develop compact heat exchangers, which are designed through numerically analyzing the boiling and condensation of low-boiling working fluids (that are in themselves complex thermodynamic phenomena), is one of the most serious factors impeding the application of ORC installations in transport vehicles. The article presents a calculation procedure for preliminary designing the heat exchangers for ORC installations represented by a refrigerant vapor generator and a refrigerant condenser. The proposed procedure, which is based on the method of successive approximations, makes it possible to take into account the variability in the thermophysical properties of the used working fluids, the specific features of heat-transfer processes, changes in the geometrical parameters of the devices, the influence of process enhancement methods, etc. The article also gives results from testing the proposed procedure for the vapor generator and condenser of an ORC installation operating with R245fa fluoroorganic working fluid. The main geometrical and thermal characteristics necessary for designing the equipment of an ORC installation that recovers the heat of exhaust gases from Type 6M32 internal combustion engines used in a shipboard installation are obtained.