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[en] The purpose of this study is to predict the performance of an indirect evaporative cooling system, and to evaluate its energy saving effect when applied to the exhaust heat recovery system of an air-handling unit. We derive the performance correlation of the indirect evaporative cooling system using a plastic heat exchanger based on experimental data obtained in various conditions. We predict the variations in the performance of the system for various return and outdoor air conditioning systems using the obtained correlation. We also analyze the energy saving of the system realized by the exhaust heat recovery using the typical meteorological data for several cities in Korea. The average utilization rate of the sensible cooling system for the exhaust heat recovery is 44.3% during summer, while that of the evaporative cooling system is 96.7%. The energy saving of the evaporative cooling system is much higher compared to the sensible cooling system, and was about 3.89 times the value obtained in Seoul
[en] This paper gives a special focus on the role of outlet temperature of flue gas (T_g_o) in organic Rankine cycle (ORC) system for low temperature flue gas waste heat recovery. The variations of performance indicators: net work (W_n_e_t), exergy efficiency (η_e_x) and levelized energy cost (LEC) versus T_g_o are discussed. Considering the corrosion of low temperature flue gas, the necessity and reasonability of limiting T_g_o at its minimum allowed discharge temperature (355.15 K) are analyzed. Results show that there exist optimal T_g_o (T_g_o_,_o_p_t) for W_n_e_t and LEC, while T_g_o_,_o_p_t for η_e_x does not appear under the investigated range of T_g_o. Moreover, the T_g_o_,_o_p_t for W_n_e_t is always lower than 355.15 K, the T_g_o_,_o_p_t for LEC, despite being greater than the one for W_n_e_t, is just slightly higher than 355.15 K when the inlet temperature of flue gas varies from 408.15 K to 463.15 K. For the waste heat recovery of low temperature flue gas, it is reasonable to fix T_g_o at 355.15K if W_n_e_t or LEC is selected as primary performance indicator under the pinch point temperature difference of evaporator (ΔT_e) below 20K.
[en] Highlights: • A methodology for energy efficiency of large-scale chemical plants is developed. • A multi-level data extraction for energy requirement definition is introduced. • The practice of total site integration with the combination of levels is shown. • The suitable utilities are integrated and optimized for different proposals. • A Pareto analysis is performed to find the optimum combination of levels. - Abstract: This study presents a methodology based on process integration techniques to improve the energy efficiency of a large-scale chemical plant. The key to the approach is to represent the energy requirements with different heat transfer interfaces. Considering difficulties of data extraction for a large-scale plant, a multi-level data extraction scheme is introduced based on different heat transfer interfaces and includes five levels of growing complexity: black-box, grey-box, white-box, simple-model and detailed-model analysis. A combination of these levels instead of a single definition for the energy requirement has been applied on an industrial case study. Different steps of the approach are explained in detail and their potential are highlighted. The Single Process Integration (SPI) and Total Site Integration (TSI) has been performed and revealed that a higher potential of heat recovery could be driven through the TSI. The optimized site utility integration together with heat recovery improvement scenarios have considerably increased the energy saving potential in our case study. A multi-objective optimization has also been performed to find the optimum combination of units with different energy requirement levels. In conclusion, results from our case study have indicated that using a combination of different energy requirement levels will reduce the required modification of the actual site configuration
[en] In this research, a vortex generator heat exchanger is used to recover exergy from the exhaust of an OM314 diesel engine. Twenty vortex generators with 30° angle of attack are used to increase the heat recovery as well as the low back pressure in the exhaust. The experiments are prepared for five engine loads (0, 20, 40, 60 and 80% of full load), two exhaust gases amount (50 and 100%) and four water mass flow rates (50, 40, 30 and 20 g/s). After a thermodynamical analysis on the obtained data, an optimization study based on Central Composite Design (CCD) is performed due to complex effect of engine loads and water mass flow rates on exergy recovery and irreversibility to reach the best operating condition. - Highlights: • A vortex generator heat exchanger is used for diesel exhaust heat recovery. • A thermodynamic analysis is performed for experimental data. • Exergy recovery, irreversibility are calculated in different exhaust gases amount. • Optimization study is performed using response surface method
[en] Radiation recuperator is a class of indirect contact heat exchanger widely used for waste heat recovery in high temperature industrial applications. At higher temperatures heat loss is higher and as the cost of energy continues to rise, it becomes imperative to save energy and improve overall energy efficiency. In this light, a radiation recuperator becomes a key component in an energy recovery system with great potential for energy saving. Improving recuperator performance, durability, and its design and material considerations has been an ongoing concern. Recent progress in furnace design and micro turbine applications together with use of recuperators has resulted in reduced fuel consumption, increased cost effectiveness and short pay-back time periods. Due to its high commercial value and confidential nature of the industry, little information is available in the open literature as compared to convection recuperators where results are well documented. This review paper intends to bridge the gap in literature and provides valuable information on experimental and theoretical investigations in radiation recuperator development along with identification of some unresolved issues.
[en] Highlights: • Methodology development for Total Site heat recovery with of intermediate utility. • Selection of temperature for intermediate utilities of Total Site. • Capital cost reduction for heat exchangers network design on Total Site level. • Recommendation for selection of heat exchangers design of Total Site. - Abstract: In this paper a further development of methodology for decreasing the capital cost for Total Site heat recovery by use of different utility levels is proposed. The capital cost of heat recovery system is estimated for certain temperature level of intermediate utility applying Total Site Profiles. Heat transfer area is reduced by selection of appropriate temperature of intermediate utility. Minimum of heat transfer area depends on slopes of Total Site Profiles in each enthalpy interval. This approach allows estimating the minimum of heat transfer area for heat recovery on Total Site level. Case study is performed for fixed film heat transfer coefficients of process streams and intermediate utilities. It indicates that the total heat transfer area of heat recovery can be different up to 49.15% for different utility temperatures
[en] In this study, mean streamline and Computational fluid dynamics (CFD) analyses were performed to investigate the performance of a small centrifugal steam compressor using a latent heat recovery technology. The results from both analysis methods showed good agreement. The compression ratio and efficiency of steam were found to be related with those of air by comparing the compression performances of both gases. Thus, the compression performance of steam could be predicted by the compression performance of air using the developed dimensionless parameters
[en] A new local ventilation device is actually developed in such a way to procure ventilation 'on demand' in each room, with a maximal effectiveness. It consists in a wall or window frame mounted plane-parallel box, containing two (injection and extraction) fans, an electronic control, and a heat recovery exchanger. The present paper describes the experimental investigations carried out on some single components and on the entire unit in order to characterize the aeraulic and thermal performance of the device.
[en] Highlights: • A new practical heat integration framework was developed for complex and diverse production lines. • Heat recovery was maximised by direct and indirect heat integration at zonal and factory levels. • A novel approach to stream data extraction was proposed to account for both stream capacity and availability. • A case study was carried out on a multi-product confectionery factory. - Abstract: Heat integration is a key measure to improving energy efficiency and maximising heat recovery. Since the advent of Pinch analysis in the 1980s, direct and indirect integration approaches have developed in separate domains with very few examples where both approaches are utilised together to maximise heat recovery. This paper presents a novel decision-making framework for heat integration in complex and diverse production lines, with the aim to provide the user with a step-by-step guide to evaluate all heat recovery opportunities through a combination of direct and indirect heat integration. This framework involves analysis at both the zonal level and the factory level. The proposed framework was applied to a case study based on a confectionery factory in the UK that manufactured multiple products across a diverse range of food technologies. It demonstrates that the framework can effectively identify the significant streams to be considered in the heat integration analysis, and address practical factors such as diverse production times, geographical proximity, and potential of compromise to product quality when the direct and indirect heat integration opportunities are proposed and assessed both within and between production zones. This practical framework has the potential to benefit the wider food industry and beyond
[en] Highlights: • Subcooled boiling first occurs in the inner side of helical coils under the studied test conditions. • ONB can appear in helical coils when mean wall temperature is lower than saturation temperature. • Effects of various parameters on wall temperature and HTC are studied in helical coils. • New correlations have been proposed for ONB and HTC of subcooled boiling in helical coils. - Abstract: Helical coils have been widely used in a variety of applications, such as heat recovery processes, power plants, cryogenic systems, etc, due to the practical importance of high efficiency heat transfer, compactness in structure, ease of manufacture and arrangement. Experiment investigation of heat transfer characteristics of subcooled flow boiling in helical coils with different inner diameters and coil diameters was performed in the present paper. The rise angles of these helical coils were all 6 degrees. The system pressure was in the range of 1.8 MPa and 7.8 MPa, mass flux ranged between 300 kg/(m2·s) and 1100 kg/(m2·s), and heat flux varied from 100 kW/m2 to 450 kW/m2. The experimental results showed that the onset of subcooled boiling was significantly influenced by heat flux and system pressure. A new correlation to predict the onset of subcooled boiling was proposed, correlating experimental results within ±20%. The effects of heat flux, mass flux and system pressure on heat transfer behavior in subcooled boiling region were discussed. A new correlation of subcooled boiling heat transfer coefficient in helical coils was developed, correlating experimental results within ±20%.