Analysis of the thermohydraulic parameters of the condenser–heat exchanger of a pyrolysis bioenergy plant

Abstract

Relevance: the modern development of bioenergy is driven by the need to identify sustainable and environmentally clean energy sources. Biomass pyrolysis processes are of particular interest, since they allow not only the utilization of agricultural and wood residues but also the production of valuable outputs in the form of fuels, heat, and chemical compounds. One of the key components of pyrolysis plants is the condenser–heat exchanger, which ensures efficient condensation of the vapor–gas mixture and recovery of heat. The overall energy efficiency of the installation, as well as the stability and safety of the technological process, directly depend on its performance. Under the conditions of increasing requirements for energy saving, emission reduction, and enhanced reliability of equipment, the study of thermohydraulic processes in condensers becomes especially relevant. Such analysis makes it possible to justify optimal operating parameters, improve the overall heat transfer coefficient, and reduce hydraulic losses, which ultimately contributes to the development of more efficient and environmentally oriented bioenergy technologies.

Aim: analysis of the thermohydraulic characteristics of a condenser–heat exchanger of a pyrolysis-based bioenergy system considering phase transitions of the vapor–gas mixture. The study is aimed at substantiating the optimal operating parameters and enhancing heat transfer efficiency while simultaneously reducing hydraulic losses.

Methods: analytical calculation methods, empirical correlations, Xin–Ebadian correlations, regression analysis methods, experimental measurements using thermocouples, a manometer and a pyrometer, as well as numerical modeling in the COMSOL Multiphysics environment were employed.

Results: it has been established that the overall heat transfer coefficient of the condenser strongly depends on the mass flow rate of the cooling water and the temperature driving force between the pyrolysis gas–vapor mixture and the coolant. With an increase in water flow rate, the heat transfer coefficient rises from 165.7 to 193.3 W/m²·K. The calculated data show good agreement with the experimental results, and the condensation zone maps revealed that the highest heat transfer intensity occurs at the inlet of the gas–vapor mixture, gradually decreasing along the coil length, which provides a basis for justifying the rational design parameters and operating conditions of the condenser.