Design Of Heat Recovery System Research Articles

A novel design of heat recovery system from exhaust stacks' silencers in a simple cycle gas turbine

This paper aims to evaluate the potential of heat recovery from the integrated heat exchanger within the exhaust stack silencer baffles in a simple cycle gas turbine. Heat transfer channels were incorporated into the upstream (nose) and downstream (tail) sections of the parallel silencer baffles in the exhaust stack. The gas turbine exhaust gas represents the hot side flow across the baffles' sections. The integrated heat exchanger system offered an advantage of extracting waste heat from the exhaust stream, while reducing pressure drop on the flow and improving acoustic attenuation.In this work, a series of parametric studies were carried out across a range of internal and external heat transfer area configurations within the silencers to maximize the heat transfer. Further enhancement opportunities were introduced and discussed based on the conducted parametric studies and practical aspects borne out of common industry practice. The proposed heat recovery system was implemented to power the gas fuel performance heater which is used to enhance the gas turbine cycle performance through utilization of the extracted waste heat while keeping lower exhaust pressure drop in the stack.The obtained results showed that the proposed integrated heat exchanger within the silencers has a potential of generating a 5.48 MW net gain from the gas turbine exhaust stacks which are normally lost to the atmosphere from the simple cycle exhaust stack. The proposed heat recovery system proved significant fuel savings that lead to economic benefits and reduction in CO2 emissions.

Load characteristics analysis of the water source heat pump heating system using data center waste heat

The number and scale of data centers (DCs) in China are constantly expanding with the advancement of networking and informatization. A large amount of waste heat is dissipated at its end. If this waste heat can be recovered, then achieving carbon neutrality in DCs can be effectively accelerated. At present, water source heat pump (WSHP) are widely used in air-cooled and liquid-cooled DCs of different sizes for waste heat recovery. This study analyzes the equipment type and heating capacity of different brands of WSHP units. Three WSHP heating systems are proposed according to the different locations of waste heat enhancement (SE, TDE, UE). The coupling and matching relationship between user-side heat load demand, DC waste heat load, and energy efficiency of WSHP units under different systems is also investigated. Moreover, the law of energy consumption and energy efficiency changes is analyzed. Thus, this study provides a reference for the DC waste heat recovery system design and equipment development. The results show that the coupling matching relationship between user-side heat load demand, DC waste heat load, and heating COP of WSHP units is Q.N/Q.S=COP′/COP′-1=φ, where φ ranges from 1.1962 to 1.3642. The heating COP of the SE system is the greatest when user-side heat load demand is between 0 and 120 kW. The heating COP of the TDE system is the highest when the user-side heat load demand is between 1750 and 70000 kW. Furthermore, the heating COP of the three WSHP heating system types is related to unit brand when user-side heat load demand is between 120 and 1750 kW.

Integrated Heat Regenerator (IHR) Designs with Hydrogen Preheater and Thermoelectric Generator for Power Enhancement of a 2 kW Fuel Cell Vehicle

The power train efficiency of fuel cell vehicles (FCV) can be enhanced by improving the hydrogen energy utilization. Based on a mini FCV running on a 2 kW open-cathode Polymer Electrolyte Membrane (PEM) fuel cell, a waste heat recovery system design needs to be developed as an approach towards higher energy efficiency. The novelty of the system is on the integration of thermoelectric generator technology with hydrogen preheating process for a combined heat and power output. This manuscript presents the proposed integrated heat regenerator (IHR) designs, analysed using numerical computational modelling. Three IHR designs were proposed where the main design criteria are (i) a minimum of 10oC hydrogen preheating degree, and (ii) non-parasitic active cooling for the Thermoelectric generator (TEG) cells. Three design concepts were studied to identify its design and performance limitations. The numerical results were validated with theoretical modelling analysis for hydrogen exit temperatures and TEG surface temperatures. The analysis on predicted fuel cell power enhancement, TEG power generation and waste heat utilization were performed by relating the temperature profiles of the hydrogen reactant and TEG surfaces to fuel cell reaction models and TEG power relationships. A compact IHR design that produced 7.7 to 8 % total power enhancement and suitable in size for a mini FCV was identified for future development works

Heat integration of power-to-heat technologies: Case studies on heat recovery systems subject to electrified heating

A systematic design methodology for the electrified supply of heat in process industries is developed to provide process design guidelines for economic and energy-efficient transition from a fossil-fuelled energy system to a renewable-based electricity system. The most appropriate strategy for the implementation of electrified sources for energy systems is proposed in the context of Heat Integration. Design implications related to the introduction of electrified sources for industries are fully investigated for the design of heat recovery systems between conventional fossil-fuelled systems and electrified systems. As the electricity-based heating systems allows more degrees of freedom for the design of the HEN (Heat Exchanger Network) than fossil-fuel-based systems, design complexities of HEN under electrification can be considerably reduced. This is illustrated with a few cases of heat recovery system in which capital cost and design complexities can be minimized by considering the electrified energy supply and their characteristics in an effective and integrated manner. Preliminary techno-economic assessment for electrified energy recovery systems is carried out to understand economic limitation of industrial electrification under current energy prices and its sensitivities.

EXERGY BASED SUSTAINABILITY ASSESSMENT OF AN ORC INTEGRATED WASTE HEAT RECOVERY SYSTEM FOR MARINE VESSELS

This paper introduces the basics of exergy based sustainability assessment and the framework that should be shaped within in the first stage. The sustainability assessment framework leads to sustainability indicators that are used to assist policy makers and decision-making processes. The literature review shows that the energy systems are suited to sustainability assessment with exergy based assessment tools and indicators from an environmental point of view. In this study, an exergy based sustainability assessment is carried out by using the exergy analyses results of an ORC (organic Rankine cycle) integrated waste heat recovery system on a 1,221 TEU container ship. The exergy analysis results are used to derive comparable and quantified exergetic sustainability indicators that indicate the sustainability level and further improvement potentials with the utilization of the proposed waste heat recovery system design. The assessment results show that the minimum waste exergy ratio is obtained from R1234ze(Z) at 3 MPa with the value of 0.106. R1234ze(Z) and R245fa working fluids show good environmental performance for the proposed system design. The maximum exergetic sustainability index values are obtained from R1234ze(Z) and at 3 MPa at the value of 8.435.

Improvement of environmental conditions by applying heat recovery technologies of boiler plants

Purpose. Analysis of the effectiveness of using methods of heat and humidity treatment of flue gases to improve the operational modes of chimneys for heating gas-consuming boiler plants with heat recovery systems. Methodology. The known normative methods of thermal calculation of boiler plants and methods of dispersion of pollutants emitted by chimneys of these plants were used. To determine the thermal and moisture parameters of flue gases during their deep cooling, an original method developed at the Institute of Engineering Thermophysics of the National Academy of Sciences of Ukraine was used. Findings. The efficiency of applying the proposed thermal methods to improve environmental conditions and magnification of the operational reliability of chimneys of boiler plants equipped with systems for deep heat recovery of exhaust gases has been studied. The methods which are usually used in boiler-houses to prevent condensate formation in chimneys were considered. Adecrease in the maximum ground-level concentration of nitrogen oxides and carbon monoxide emissions was determined when using these methods. A comparative analysis of the effectiveness of the proposed methods for brick and metal chimneys in different modes of operation of heating boiler plants has been carried out. It is shown that these methods allow improving significantly (up to 32%) the indicators of ecological efficiency of chimneys in conditions of 58% reduction of fuel use in boilers. Originality. For the first time to improve the environmental performance of chimneys of boiler plants with deep heat recovery systems of flue gases has been justified the use of thermal methods of their heat and moisture treatment. Practical value. The possibility of using the results of the work in the design of heat recovery systems for gas-consuming heating boilers.

Optimization and design of heat recovery system for aviation

Heat recovery remains an active topic in energy system research because of the potential benefits in energy consumption and energy efficiency. Among the recent advances, the intercooled recuperated heat recovery concept has provided significant advancements in energy conversion for gas turbine engines. However, when applying this concept to aero engines, the lack of available space in the engine and the low tolerance for pressure loss are critical challenges in this complicated energy system. Therefore, an improved structure for a complex heat recovery energy system called the intercooled recuperated turbofan engine is proposed. In addition, a novel systematic optimization design method based on multidisciplinary theories is introduced. The new heat recovery system design is designed and analyzed with respect to the installation space and the engine performance. Because the system is very complex and strongly coupled, a sensitivity analysis has been conducted to decouple the parameters of this non-linear problem. By optimization, the structure of the engine is modified to adapt the heat recovery system′s demand for space (through a change in air flow). Its energy saving benefits are compared to a traditional turbofan engine; the new, optimized design has a lower fuel consumption. It achieves a high overall efficiency with a lower overall pressure ratio. This systematic design method is extremely important for complicated energy systems: it addresses the necessary compromises between structure and performance, which remains a critical challenge for energy systems.

COMPREHENSIVE METHODS OF EVALUATION OF EFFICIENCY AND OPTIMIZATION OF HEAT-UTILIZATION SYSTEMS

At present, Ukraine has the necessary potential for the implementation of effective energy-saving technologies for heat recovery, and therefore the problem of their development and implementation is relevant for the country's energy sector. The solution of this problem is related to the need for systematic studies of the efficiency of optimization of heat recovery facilities from the standpoint of modern methodological approaches. The paper outlines the main stages in the development of integrated methods for assessing the efficiency and optimization of heat recovery systems based on the principles of exergic analysis, statistical methods for planning the experiment, structured variational methods, multilevel optimization methods, the theory of linear systems and the thermodynamics of irreversible processes. Examples and illustrations illustrate some of the stages in the development of complex methods. The necessary general step in the development of methodologies is the development of new performance criteria. Such criteria are highly sensitive to changes in the regime and design parameters of heat recovery systems due to the inclusion of some exergic characteristics in them. The developed criteria also serve as target optimization functions. For individual elements of heat recovery systems, efficiency and optimization methods usually include the definition of the functional dependencies of the selected efficiency criteria on the main parameters. For this, balance methods of exergic analysis and statistical methods of experiment planning are used. If such dependencies are established, optimization is carried out using known mathematical methods. For complex heat recovery systems involving a large number of elements, it is not possible to establish general analytical dependencies of the optimization objective functions on the parameters of the system when constructing mathematical models necessary for their optimization. Complex methods based on the basic principles of structural-variant methods, methods of multilevel optimization, the theory of linear systems, and the thermodynamics of irreversible processes have been developed for such cases. For this purpose, structural diagrams of plants, block diagrams of multi-level optimization have been developed, complete input matrices have been constructed, mathematical models for the processes under investigation have been developed, formulas have been derived for calculating the loss of exergy power in heat conduction processes and formulas for calculating dissipators of exergy. A well-founded choice of the methodology for evaluating efficiency and optimization raises the effectiveness of optimization, since it allows the use of parameters maximally close to optimal when developing the heat recovery system design, which in turn increases the efficiency of the system. References 14, figures 5.

Optimization design of heat recovery systems on rotary kilns using genetic algorithms

Heat loss from rotary kilns accounts for certain amounts of the total energy consumption in chemical and metallurgical industries. To reduce the heat loss, a parallel and a series-parallel heat recovery systems with nine heat recovery exchangers are proposed to preheat the cold water in this paper. Experimental measurements are carried out to determine the heat transfer coefficient equations of each heat recovery exchanger. Then, the heat recovery systems are analyzed to deduce the mathematic relation between the design parameters and the system requirements, i.e. the temperatures and heat transfer rates of the nine heat recovery exchangers. The total heat transfer area, the total power consumption and the entropy generation due to heat transfer and fluid flow are set as the objective functions in four multi-objective optimization (MOO) cases. With the aid of the genetic algorithm in the Matlab 2015, the optimized operational and structural parameters are obtained. Finally, the MOO results are compared with that of the single objective optimization (SOO) method and the original values. The optimization results show that the MOO method are more suitable for the operational parameters design of the heat recovery systems compared with the SOO method. The required total heat transfer area and the total power consumption are decreased by at least 12.1% and 13.7%, respectively. Besides, as the entropy generation due to heat transfer and fluid flow decrease in the MOO cases, the corresponding heat transfer area and power consumption of the heat recovery system decrease, respectively.

A New Graphical Technique for Energy Efficient Design of Heat Recovery System in Chemical/Refining Industries

Chemical processes are energy intensive industries; the majority of energy consumed in industrial processes is mainly used for heating and cooling requirements. This results in increasing the interest in obtaining the optimum design of the heat exchanger networks to reduce the energy consumption and face the growing energy crises. Most of the published literature over the last fifty years promotes the process integration technology as a main part of the process system engineering science. Graphical Pinch Analysis method normally includes two key steps, firstly obtaining the energy targets which include the minimum energy required for the HEN design, then designing the heat exchanger network (HEN). This paper introduces a new graphical approach for the design of new heat exchanger networks (HENs) based on pinch analysis rules. The HEN is represented on a simple graph, where the cold stream temperatures are plotted on the X-axis while the driving forces for each exchanger are plotted on the Y-axis. This graphical technique can describe the energy analysis problems in term of temperature driving force inside the heat exchanger, which is an important factor in the design process as the differences in these driving forces are involved in calculating the area of heat exchangers, and consequently affecting the cost.

Energy audit and waste heat recovery system design for a cement rotary kiln in Ethiopia: A case study

This paper deals with the energy audit and heat recovery system modeling and design , taking a cement factory in Ethiopia as a case study. The system is a dry type rotary kiln equipped with a sixth stage cyclone type preheater , pre - calciner and grate cooler. The kiln has a capacity of 3 , 000 tons/day. The energy auditing has been performed based on the data collected from control volume of the kiln system for a ten - month period . The result shows that 25.23% of the total heat input is released to the environment through the preheater and an other 15.58% through the cooler exhausts. The west heat recovery system (WHRS) can produce a gross power of 5.26 MW as long as the kiln is i n operation . The generated power can cover all the electrical energy consumption of the kiln system whether there is a power supply from the grid or not. Therefore, the company can save up to 536,222.10 USD per year due to the production of clinker using their own power source and avoiding the loss sustained by the company due to power interruption from the grid

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.

Efficiency improvement strategies for the feedwater heaters network designing in supercritical coal-fired power plants

Coal will continue playing a major role in worldwide electricity generation during next years. This trend will augment CO2 emission to the atmosphere. Improving power plant efficiency could alleviate the negative effect of coal consumption on CO2 emissions. Main efforts have been focused on supercritical boiler technology (once-through units) and materials development (austenitic steels) with the aim of accomplishing high steam parameters that allow this efficiency enhancement. However, improvement in supercritical steam parameters should be followed by an exhaustive review of the steam cycle design. This paper shows a strategy for the optimization of the feedwater heaters network and the flue gas heat recovery system design. Starting with the lay-out of a supercritical steam cycle using the best available technology, this paper analyses not only the steam cycle itself, but also its integration with the boiler cold-end. By means of thermodynamic optimization it is possible to propose new feedwater heat exchanger network configurations and reducing steam consumption from turbine bleeds, achieving optimum power plant efficiency. Simulations have been carried out using Aspen Plus software and optimization procedure is based on a sequential quadratic programming method that maximized overall plant efficiency taking turbine bleeds pressure as independent variables. Results show a feasible improvement of the overall plant efficiency of 0.7 points in comparison with state-of-the-art reference plant. This increase implies a direct reduction of CO2 emissions of about 1.3% compared with the best plant currently available. Moreover, an economic analysis confirms the feasibility of the proposals analysed and shows important additional yearly incomes.

Heat Recovery from Urban Wastewater: Analysis of the Variability of Flow Rate and Temperature in the Sewer of Bologna, Italy

Domestic wastewater were characterize by higher temperature because inside the buildings 60% of the water was heated by showers, tubs, sinks, dishwashers and clothes washers. This heat, nowadays lost into the sewer system, could be make the wastewater a carrier of heat. This heat can be reused, for the production of clean and regenerable thermal energy, through heat exchangers and heat pumps, for the conditioning and heating of buildings. There are several options to recover this heat embedded in the wastewater: within houses (small scale applications), from the sewer (medium scale applications), or at wastewater treatment plants (large scale applications). In this paper results of a monitoring period of six months in the sewer system of Bologna (Italy) have showed the variability of wastewater flow rate and temperature and their daily trend. The trend of the flow (ratio between the hourly flow and the medium daily flow) for the generic day is linked with the population, with coefficients that are in the range of 0.25 - 1.50 with peak values ranging between 1.30 and 1.50; the trend of the sewage temperature for the generic day has coefficients in a range between 0.90 and 1.05, and it is independent by the population. The amount of thermal energy that can be obtained from wastewater and the optimally design of heat recovery systems depend on knowledge of the flow rate and wastewater temperature. This study can be useful to map the potential thermal energy of sewage systems and to design the heat recovery systems.

Heat recovery from urban wastewater: Analysis of the variability of flow rate and temperature

Heating, cooling and domestic hot water supply represent the biggest share of energy demands in residential buildings. Usually for these demands fossil fuels are used, however in the last years international energy policies recommended the use of less valuable energy. This paper investigated the possibility to use sewer water as alternative source of heat. Wastewater deriving from buildings is characterized by higher temperature than clean water because inside the buildings 60% of water is heated. The amount of energy that can be obtained from wastewater and the optimal design of heat recovery systems depend on knowledge of the flow rate and the temperature. In this paper the sewer system in Bologna (Italy) is taken as case study. Results of a monitoring period have showed the variability of wastewater flow rate and temperature and their correlation. Data analysis allowed to identify the daily trend for the wastewater flow, whose coefficients in relation to the average flow (where average flow=1) vary between 0.25 and 1.50, and for the wastewater temperature in which the coefficients ranging from 0.90 to 1.05. This study can be useful to map the potential thermal energy of sewage systems and to design of heat recovery system.

Heat and Mass Transfer Analysis of Mine Exhaust Air Heat Exchanger

As a good energy resource, Mine exhaust air has an important value of recycling. In this paper, the heat and mass exchange mechanism and potential of the mine exhaust air heat exchanger (MEAHE) is mainly researched. The heat exchanger efficiency is affected by water and air temperature and flow in terms of double efficiency method. The result can provide the basis for the further determine the thermal calculation method for MEAHE, and lays the foundation for the mine comprehensive utilization of waste heat recovery system design.

Experimental investigation on heat recovery from condensation of thermal power plant exhaust steam by a CO2vapor compression cycle

SUMMARY In this paper, a method that utilizes CO2 vapor compression thermodynamic cycle to recover low-temperature heat from exhausted water steam of fossil fuel thermal power plants is reported. Experimental investigation was carried out to study the characteristics of low-temperature heat recovery by liquid CO2 evaporation process from vacuum exhausted steam condensation occurring at the turbine exit. Furthermore, measured heat recovery performances over one whole year are presented and discussed. Experimental results show that the present heat recovery process by CO2 vapor compression cycle is able to operate stably. The yearly averaged water temperature at the CO2 condenser outlet was measured at 87.5 °C with a COP value above 5.0. This high energy efficiency ratio is found to be mainly due to two factors: the transcritical CO2 vapor compression and steam condensation phase change occurring on the CO2 evaporator. The findings from this paper provide helpful guidelines for low-temperature heat recovery system design and improving fossil fuel utilization efficiency. Copyright © 2013 John Wiley & Sons, Ltd.

Design to Maximize Performance of a Thermoelectric Power Generator With a Dynamic Thermal Power Source

It is a difficult technical challenge to design thermoelectric power generation systems that work optimally over a broad dynamic range of thermal input power. Conventional systems are designed to work optimally for a nominal operating condition, while maintaining the ability to operate at off nominal and extreme operating conditions without damage to the system. For systems that operate in a narrow range of thermal power conditions, thermoelectric waste heat recovery system design is simplified. However, for applications that do have a wide range of operating conditions, designs typically exhibit overall average efficiencies that are reduced by approximately 20% or more compared with that achievable for the thermoelectric material operating at peak efficiency. Both cars and trucks consume significant fuel at low mass flow rates. Since the ultimate goal of waste heat recovery systems is to minimize fuel consumption, it is critical that the recovery system be designed to operate near peak efficiency over the range of mass flow rates that make a significant contribution to overall power recovery. Such performance capability is especially important in city driving, and in hybrid vehicle applications. This paper describes a design concept that maximizes the performance for thermoelectric power generation systems in which the thermal power to be recovered is from a fluid stream (e.g., exhaust gas) subject to varying temperatures and a broad range of exhaust flow rates. The device is constructed in several parts, with each part optimized for a specific range of operating conditions. The thermoelectric system characteristics, inlet mass flow rates and fluid temperatures, and load and internal electrical resistances are monitored and generator operation is controlled to maximize performance. With this design, the system operates near optimal efficiency for a much wider range of operating conditions. Application of the design concept to an automobile is used to show the benefits to overall system performance.

Alternative Design Approach for Multipass and Multi-Stream Plate Heat Exchangers for Use in Heat Recovery Systems

This work presents an alternative approach for the preliminary design of plate and frame heat exchangers in complex flow arrangements and looks at the use of this type of exchanger in multi-stream applications. The need for a new design approach arises from the fact that most current design algorithms are industrially owned and thus are not readily available to the practicing engineer. The essential information required for the design of plate and frame heat exchangers are the heat transfer and friction performance data, which again are industrially owned. However, a few correlations for the most common type of plates have been reported in the open literature and, in this work, are used for the development of a design approach that exploits the concept of full utilization of allowable pressure drop. This method can be used as a first estimate for the determination of the surface area requirements of single-phase, two-stream heat exchangers. It is shown how the approach can be extended to the targeting and design of heat recovery systems or multi-stream exchangers where plate heat exchangers are a suitable option.

Residential Experience with Proton Exchange Membrane Fuel Cell Systems for Combined Heat and Power

As part of a one-year Department of Defense demonstration project, proton exchange membrane fuel cell systems have been installed at three residences to provide electrical power and waste heat for domestic hot water and space heating. The 5kW capacity fuel cells operate on reformed natural gas. These systems operate at preset levels providing power to the residence and to the utility grid. During grid outages, the residential power source is disconnected from the grid and the fuel cell system operates in standby mode to provide power to critical loads in the residence. This paper describes lessons learned from installation and operation of these fuel cell systems in existing residences. Issues associated with installation of a fuel cell system for combined heat and power focus primarily on fuel cell siting, plumbing external to the fuel cell unit required to support heat recovery, and line connections between the fuel cell unit and the home interior for natural gas, water, electricity, and communications. Operational considerations of the fuel cell system are linked to heat recovery system design and conditions required for adequate flow of natural gas, air, water, and system communications. Based on actual experience with these systems in a residential setting, proper system design, component installation, and sustainment of required flows are essential for the fuel cell system to provide reliable power and waste heat.