Analysis Of Heat Recovery System Research Articles

Performance Analysis of Heat Recovery System for a Turbofan Engine using Intercooler and Recuperator via Aspen Plus

Global warming and climate change have been major problems in the present world. Greenhouse gas emissions contribute to global warming in which carbon dioxide being the best known. The aviation sector (excluding aerospace) has contributed to a total of 49.4 billion tons of carbon dioxide emission in 2016 alone. A solution to curb the increase of greenhouse gases has been proposed to temporarily solve this problem while future technological advancements occur. Having a heat recovery system by using heat exchangers in the engine helps to not only improves the performance of the engine but to also reduce temperature of the exhaust gases that will be eliminated as waste heat into the atmosphere. The main objective of the introduction of intercoolers and recuperators is to reduce the thrust specific fuel consumption whilst increasing the thrust and reducing emissions. This research thesis focuses on the analysis of intercooling and recuperation within the aspects of thermodynamics to be integrated into a typical turbofan engine. The analysis will be conducted via process simulation software – Aspen Plus V11 and the data from the software will be exported to Microsoft Excel for post-processing and graph visualization. Three main objectives of the study are to determine whether compression work will be reduced, studying the increase of thrust and performance of the engine with the positioning of heat exchangers and the improvement of TSFC with the integration of heat exchangers. For the first objective, it has been proven that there is a reduction in compression work for the recuperated engine of 7.64% but there is a 13.17% increase in compression work for the intercooled engine. For the second objective, thrust increased in both recuperated and intercooled cycles with 1.14% and 1.31% for the recuperated and intercooled cycles, respectively. Finally for the third objective, a decrease in TSFC for both recuperated and intercooled cycles show that both the heat recovery systems have an improvement of TSFC.

Multi-stage heat-pipe heat exchanger for improving energy efficiency of the HVAC system in a hospital operating room 1

Abstract The demands of specific requirements related to thermal comforts, such as temperature, relative humidity, inside air exchange and other factors required in a hospital operating rooms, have necessitated the development of energy-efficient heating, ventilation and air conditioning (HVAC) systems and efficient heat-recovery system using a heat-pipe heat exchanger (HPHE). The experiment was conducted by using HPHEs having three, six and nine rows, with four heat pipes in each row, arranged in a staggered configuration with a variation of fresh-air inlet temperature and velocity. The theoretical analysis was conducted using the ε-NTU method for predicting the effectiveness, outlet temperature of the evaporator side and energy recovery of the HPHE. The experimental results indicated that increasing the air-inlet temperature in the evaporator section and the number of rows increased the HPHE effectiveness but increasing the air-inlet velocity reduced the effectiveness. The highest effectiveness of 62.6% was obtained at an air-inlet temperature of 45°C with an air-inlet velocity of 2 m/s and a 9-row HPHE. The energy recovery of the HPHE increased with the number of rows, air-inlet temperature and air velocity in the evaporator section. The ε-NTU method can be used as a comparison method in the analysis of heat-recovery systems that apply HPHE air conditioning systems. Heat pipes that utilize cold-air exhaust from a room in an HVAC system can enhance efficiency and reduce emissions.

Key issues and novel optimization approaches of industrial waste heat recovery in district heating systems

Large amount of low-grade waste heat is discharged into the environment during industrial processes. This part of waste heat can be collected to serve district heating systems as an important heat source. In most studies of industrial waste heat recovery, the proposed system simulations were unsophisticated in terms of analyzing the real processes. For this reason, the tangency analysis has recently been proposed, and it has been found effective in conducting optimization analysis for direct-heat-exchange systems with multi-heat sources. However, in this study, it has been found that the tangency method has limitations in designing systems with heat pumps, and therefore the disadvantages of tangency analysis are suggested and discussed. Exergy analysis reveals that without considering additional exergy generated by heat pumps, the systems designed by tangency technology tend not be the optimal configuration when heat pumps are employed. In this study, the process optimization principles have been developed from the exergy analysis of heat recovery systems with heat pumps. The optimization principles and mean-heat-transfer-times index are proposed as the key point of process design. Based on the principles, two specific optimization methods in graphic expression are suggested. In the case studies, energy input decreased by more than 70%, which compares favorably with that of tangency analysis.

Design and analysis of heat recovery system in bioprocess plant

The paper deals with the heat integration of a bioprocess plant which produces yeast and ethyl-alcohol. The referent plant is considered to be a multiproduct batch plant which operates in a semi-continuous mode. The design of a heat recovery system is performed by batch pinch analysis and by the use of the Time slice model. The results obtained by direct and indirect heat integration approaches are presented in the form of cost-optimal heat exchanger networks and evaluated by different thermodynamic and economic indicators. They signify that the heat recovery system without a heat storage opportunity can be considered to be a more profitable solution for the energy efficiency increase in a plant.

A new graphical method for Pinch Analysis applications: Heat exchanger network retrofit and energy integration

Energy integration is a key solution in chemical process and crude refining industries to minimise external fuel consumption and to face the impact of growing energy crises. Typical energy integration projects can reach a reduction of heating fuels and cold utilities by up to 40% compared with original designs or existing installations. Pinch Analysis is a leading tool and regarded as an efficient method to increase energy efficiency and minimise fuel flow consumptions. It is valid for both natures of design, grassroots and retrofit situations. It can practically be applied to synthesise a HEN (heat exchanger network) or modify an existing preheat train for minimum energy consumption. Heat recovery systems or HENs are networks for exchanging heat between hot and cold process sources. All heat transferred from hot process sources into cold process sinks represent the scope for energy integration. On the other hand, energies required beyond this integrated amount are to be satisfied by external utilities. Graphical representations of Pinch Analysis, such as Composite and Grand Composite Curves are very useful for grassroots designs. Nevertheless, in retrofit situation the analysis is not adequate and besides it is graphically tedious to represent existing exchangers on such graphs.This research proposes a new graphical method for the analysis of heat recovery systems, applicable to HEN retrofit. The new graphical method is based on plotting temperatures of process hot streams versus temperatures of process cold streams. A new graph is constructed for representing existing HENs. For a given network, each existing exchanger is represented by a straight line, whose slope is proportional to the ratio of heat capacities and flows. Further, the length of each exchanger line is related to the heat flow transferred across this exchanger. This new graphical representation can easily identify exchangers across the pinch, Network Pinch, pinching matches and improper placement of fuel consumption. Furthermore, such a graph can recognise promising modifications to improve the energy performance and hence less fuel and cooling water requirement. Graphs developed in this work can be used to analyse the energy performance of existing networks with respect to energy targets. They can also be used in junction with the background process to modify basic designs or existing network for better energy integration opportunities and minimum fuel demands. The application of the new graphical method to a case study showed savings of approximately 17% in energy demands and fuel consumption.