Recovery Heat Exchanger Research Articles

Methanol synthesis through CO2 capture and hydrogenation: Thermal integration, energy performance and techno-economic assessment

This work assesses the opportunity of using “green” methanol (MeOH) produced from renewable electricity as a vector for the decarbonization of chemical process industry. We developed a comprehensive process model to simulate all the relevant sections for the conversion of 1.25 t/h of captured CO2 from a coal-fired power plant to methanol, using “green” hydrogen via water electrolysis. We applied the pinch analysis methodology for an improved thermal management of the integrated carbon capture, electrolysis and methanol synthesis plant. A network of recovery heat exchangers was designed with the pinch analysis methodology, allowing a thermal energy saving of 4.59 MW, with a net reduction of heating and cooling demands by 81 % and 47 %, respectively, and an improvement of the global efficiency of the plant from 26.74 % to 37.22. We followed a bottom-up approach for the techno-economic assessment, defining a confidence range for the main indicators of system economic viability. We assessed their sensitivity to the cost of electricity from seven renewable energy sources and to the option of selling oxygen produced by water electrolysis, in three different cost scenarios (1-optimistic, 2-realistic, 3-pessimistic). The estimated values of the cost of methanol (COM) span from a maximum range of 2624–2706 €/t (in the case of concentrated solar power) to a minimum of 565–647 €/t (hydropower with highest valorization of electrolytic oxygen), hence resulting in line with the future trends of methanol market price (400–800 €/t) in five of the considered configurations. We have finally estimated the levelized cost of methanol (LCOM) ensuring an internal rate of return ranging from 0 to 10 % for each of the techno-economic scenarios identified. Assuming 10 % as the target, LCOM in case of hydropower as renewable energy source spans from 874 to 1356 €/t, hence close to the future market price of MeOH with margin of improvement (655–1135 €/t) in case of lower costs of electric energy.

Applications and technological challenges for heat recovery, storage and utilisation with latent thermal energy storage

Thermal energy storage (TES) technology is considered to have the greatest potential to balance the demand and supply overcoming the intermittency and fluctuation nature of real-world heat sources, making a more flexible, highly efficient and reliable thermal energy system. This article provides a comprehensive state-of-the-art review of latent thermal energy storage (LTES) technology with a particular focus on medium-high temperature phase change materials for heat recovery, storage and utilisation. This review aims to identify potential methods to design and optimise LTES heat exchangers for heat recovery and storage, bridging the knowledge gap between the present studies and future technological developments. The key focuses of current work can be described as follows: (1) Insight into moderate-high temperature phase change materials and thermal conductivity enhancement methods. (2) Various configurations of latent thermal energy storage heat exchangers and relevant heat transfer enhancement techniques (3) Applications of latent thermal energy storage heat exchangers with different thermal sources, including solar energy, industrial waste heat and engine waste heat, are discussed in detail.

Investigation of the use of various materials for the construction of an enthalpy exchanger

Abstract Considering the current gradual depletion of non-renewable primary sources, it is necessary to address the reduction of energy consumption in ventilation and air conditioning systems. Although heat recovery alone reduces the energy intensity of these systems, if moisture recovery is considered as well, the contribution in reducing energy consumption is significant. These are mainly the devices designed primarily for spaces where people stay permanently, which do not allow large fluctuations in temperature and humidity. In cooperation with the manufacturer of heat recovery exchangers, we determined our own method of comparing different types of materials that could be used to design an exchanger which would also allow moisture recovery. These results in a significant reduction in energy consumption used to humidify the air in ventilation and air conditioning systems. It is one of the possible ways how to compare individual samples that are being measured. This article primarily deals with the comparison of three different types of materials, out of the total number of twelve measured samples.

Experimental Investigation on Triple Concentric Tube Heat Exchanger with Helical Baffles

A heat exchanger is a device used to transfer thermal energy between two or more liquids, between a solid surface and a liquid, or between solid particles and a liquid at different temperatures and in thermal contact where shell and tube heat exchangers contain a large number of tubes packed in a jacket whose axes are parallel to those of the shell. Heat transfer occurs when one fluid flows into the pipes while the other flows out of the pipes through the jacket. In industry, three-tube heat exchanger tubes are used as condensers, evaporators, sub cooler, heat recovery heat exchangers, etc. The three concentric tube heat exchanger is a constructively modified version of the double concentric tube heat exchanger as an intermediate tube adds some advantages over the double tube heat exchangers in that it is larger tube surface area heat transfer per unit of length. In the present study, the triple tube heat exchanger is further modified by inserting helical baffle over the surface of one of the tubes and observed turbulence flow which may lead to high heat transfer rates between the fluids of heat exchanger. Further, the Reynolds number, Nusselt number, friction factor of the flow at different mass flow rates of the hot fluid while keeping a constant mass flow rate of cold and normal temperature fluids were calculated. It was found that as the mass flow rate of the fluid increases the Reynolds number increases, the turbulence in the flow will increase which will cause the intermixing of the fluid, higher the rate of intermixing, more will be the heat transfer of the system.

Technology for Block Design of a Gas Treatment Plant for Oil Blow-Off to Remove Hydrogen Sulfide

A technology is proposed for block design of a complex for purifying the oil blow-off gas to remove hydrogen sulfide by absorption desulfurization with chelate iron complexes. The complex consists of the following blocks: block of input separators for separation of hydrocarbon condensate and protection of the stripping column from volley discharges of oil; the unit for purifying blow-off gas to remove hydrogen sulfide and mercaptans; drying unit for purified blow-off gas and a block for producing sulfur. During operation of the plant, the gas to be cleaned is mixed with blow-off and regeneration gas and washed in the absorber with a regenerated chelate absorbent to obtain the purified gas and saturated absorbent. The absorbent is sent to the degassing and clarification device, from which the blow-off gas, clarified absorbent and sulfur suspension are removed. The sulfur suspension is fed to the device for washing with water condensate and/or steam to obtain wash water and washed sulfur suspension, which is fed through a recovery heat exchanger and a heater in the separator from which liquid sulfur and desulfurized water are removed. The clarified absorbent is mixed with the circulating regenerated absorbent and fed to the regenerator, where the air is purged and the exhaust air is removed. The regenerated absorbent is divided into a circulating stream and balance stream, which, after mixing with the washing and desulfurized water, is fed to the absorber as a regenerated absorbent. The proposed complex allows to reduce the loss of the absorbent and reduce energy costs, to obtain commercial oil and fuel gas purified of hydrogen sulfide for transportation through gas pipelines.

Exhaust Gas Heat Exchanger Design Based on the Engine Backpressure and Heat Rate Criteria

The use of shell and tube heat exchangers for waste heat recovery has shown excellent results in increasing engine performance, as well as offering a large surface area for small volumes, ease of cleaning, good mechanical layout, and well-known design procedure. This article presents the modeling of the coupling circuit and thermo-fluid design of the heat exchangers in the thermal oil circuit in order to maximize the heat transfer of this equipment at the lowest pressure drop and acquisition cost, which is obtained with a smaller heat transfer area. The research results show the existence of optimal values for the studied system parameters, type of organic working fluid, type of heat exchangers, besides the size of the other system components, which are particular for the studied application. However, these results cannot be compared with the real projects already implemented in the industry due to their absence. It has been verified that the fluids that have showed the best performance in terms of thermal efficiency have been acetone and benzene, with an overall thermal efficiency of 17% and 15%, respectively.

System impact of heat exchanger pressure loss in ORCs for smelter off-gas waste heat recovery

Applying Rankine cycles to smelter off-gas could increase the required off-gas fan power in an order of magnitude equivalent to the power production. Predicting the fan power is not straightforward since it is affected in two contradictory ways: 1) the heat recovery heat exchanger creates additional off-gas pressure loss, increasing fan power; 2) off-gas cooling reduces pressure loss in the off-gas handling system downstream of the cycle, reducing fan power. The purpose of our study is to analyze the effect of fan power on optimum system performance. While additional fan power can be calculated based on heat exchanger pressure loss, the reduction in fan power depends on the total pressure loss downstream of the cycle, which is unknown. As an alternative to calculating fan power reduction, we account for the off-gas cooling effect by including only parts of the fan power caused by heat exchanger pressure loss. Results from three cases show that both heat exchanger and cycle performance strongly depend on the potential for downstream pressure loss reduction. Thus, the total pressure loss in the downstream off-gas handling system has a significant impact on the optimum heat exchanger and cycle performance, and should be accounted for during system design.

EXPERIMENTAL TEST STAND OF A HEAT PUMP INTEGRATED IN AIR HANDLING UNIT

Heat pumps are becoming increasingly popular and are playing an important role in the heat and cooling supply chain of buildings sector. Although more than 160 years have passed since the manufacture of the first heat pump, this technology, designed to recover low­potential heat energy and its useful use, can be called an innovative and efficient energy transformer. Air­to­water and air­to­air heat pumps are becoming more popular today due to their installation cost compared to ground­to­water heat pumps. It has been noticed that recently air­to­air heat pumps are more often installed in modern air handling units. The main energy transformers in these air handling units are the air­to­air heat pump and recovery heat exchanger. In the scientific literature little attention is paid to the thermodynamic cycle of the combination of the air handling unit and the heat pump, as well as the search for new possibilities to change and control it, this is a potential direction that can increase the efficiency of the whole system. To study the control capabilities of the unit, an experimental stand of the heat pump built into the ventilation unit is needed; it would help validate the results of theoretical studies and investigate the possibilities of expanding the control. Therefore, this paper presents a review of the experimental stands of non­integrated heat pumps and integrated heat pumps in air handling unit. Based on this review, the basic requirements for the installation of an experimental stand of a heat pump built into an air handling unit are formulated and a conceptual scheme of this stand is drawn up.

Advances in multifunctional balanced ventilation technology for dwellings and arising challenge to quantify energy efficiency and renewable generation contributions using international test standards

This paper evaluates the ability of EN16573:2017 to isolate and quantify the energy efficiency and renewable generation contributions of multifunctional balanced ventilation systems. These systems integrate an air-source heat pump with heat recovery ventilation and two similar, yet physically different configurations (C1 and C2) are assessed. Heat pump operation does not influence heat recovery performance for widely used configuration C1 but does influence for novel configuration C2. This study shows that while EN16573:2017 can isolate the energy efficiency (heat recovery exchanger) and renewable generation (heat pump) contributions for configuration C1, it fails when applied to configuration C2. Measurements undertaken using EN16573:2017 on configuration C2 revealed an overall coefficient of performance of 5.07, split 51% heat exchanger with heat pump off (phase 1), and 49% heat pump (phase 2 minus phase 1). If this result were obtained for configuration C1 the respective contributions would be 51% energy efficiency and 49% renewable generation. While these contributions cannot be resolved using EN16573:2017 for configuration C2, it can be achieved using two additional measurement planes in the incoming airstream. These showed an 88%:12% contribution from the heat exchanger and heat pump, respectively. While accurate, this result under-estimates the true heat pump contribution, as its positive impact on the heat exchanger efficiency boosts its contribution from 51% (phase 1) to 88% (phase 2). This paper acknowledges that heat pump operation leverages a 37% increase in heat exchanger performance and proposes a that the respective contributions of the heat exchanger and heat pump should be 42%:58%.

Investigation of fouling mechanisms for diesel engine exhaust heat recovery

The effect of diesel engine exhaust fouling on heat and mass exchangers for waste heat recovery is investigated. Experiments are conducted for a range of operating conditions relevant to the use of the waste heat from a diesel engine for powering a 2.71 kW capacity absorption heat pump. Thermal resistances of fouling layers as well as their effects on pressure drop are determined, and the underlying mechanisms for deposition and removal are investigated. Fouling layer effects are most severe for the lowest coolant temperatures and 100% generator load. At these conditions, the fouling thermal resistance is approximately 70% of the total resistance, and the ratio of the steady-state pressure drop to the baseline pressure drop is 3.25. Flow induced shear is found to be the primary growth inhibiting mechanism at high exhaust velocities. Results from this study can guide heat exchanger design for a variety of waste heat recovery systems.

Deposition characteristics of particles in inclined heat exchange channel with surface ribs

Ash particles in flue gas flow would deposit on the heat recovery exchanger in the waste heat recovery system (WHRS), which may lead to the reduction of heat transfer efficiency and service life. Understanding of ash particle deposition in the heat exchange channel is crucial for the safe operation of WHRS. In this study, deposition characteristics of ash particles in an inclined heat exchange channel with surface ribs were investigated by using Reynolds stress model combined with discrete phase model. The turbulent fluctuation correction and particle rebound model were developed by using UDF program to improve the prediction accuracy. After grid sensitivity analysis and numerical verification, the flue gas thermal-fluid fields, the 3D particle deposition patterns and deposition efficiency on each ribbed channel surface were obtained and analyzed. Parameter study on the deposition characteristics was conducted by considering flue gas flow velocity, particle size and inclination angle of the ribbed channel. The results showed that significant secondary flow eddies can be observed near the rib windward surfaces and high-value turbulent intensity area appears near the rib crest. The windward surfaces and the crests of the ribs are the main deposition locations in the inclined heat exchange channel. The deposition efficiency in the ribbed channel is obviously changed by the particle diameter and flue gas flow velocity. The inclination angle has little influence on deposition efficiency for small particles (dp<5μm) but great effect on deposition efficiency for large particles (dp>10μm).

Experimental characterization of a novel soft polymer heat exchanger for wastewater heat recovery

Wastewater released from showers, sinks, and washers contains a considerable amount of waste heat that can be recovered by using a heat exchanger. Conventional metal heat exchangers for wastewater heat recovery have common problems of corrosion, fouling and clogging, which makes it necessary to develop a new type of heat exchanger for such low-grade thermal energy recovery applications. This study deals with a novel patented polymer heat exchanger (WO2020049233A1) made of soft polyurethane tubes that are capable of oscillation once subjected to external forces. Laboratory tests coupled with theoretical analyses show a stable global heat transfer coefficient of 100-110 W/m2·K, achieving 67-92% of the performance of titanium-, aluminum-, and copper-made heat exchangers with the same configuration. It further reveals that the performance of the soft heat exchanger can be enhanced by 30% when it is under oscillation. In addition, the external convective thermal resistance appears to be the dominant one instead of heat conduction through the wall material. The special operating condition of heat recovery from a sewer pipeline makes the polymer heat exchanger particularly adapted with its equivalent thermal performance but advantages of high flexibility, modularity, and low cost.

Techno-economic assessment of waste heat recovery enhancement using multi-channel ceramic membrane in carbon capture process

This study retrofitted the rich-split carbon capture process by introducing a commercial multi-channel ceramic membrane heat exchanger (Multi-CMHE) for waste heat recovery from the stripped gas vented from the CO2 stripper. The parametric study and economic analysis were conducted to comprehensively evaluate the feasibility, adaptability, and net profit of Multi-CMHE-modified rich-split monoethanolamine-based carbon capture process. Results showed that a large pore-sized Multi-CMHE has a low mass transfer flux but a high heat transfer flux. An increase in the bypassed CO2-rich solvent flow rate, water vapor molar fraction in the stripped gas and total gas pressure in addition to a decrease in the CO2-rich solvent temperature can greatly enhance the heat recovery performance. The maximum specific heat recovery can reach up to 1423.3 kJ/kg-CO2 for the 30 nm pore-sized Multi-CMHE. Furthermore, an economic analysis of the Multi-CMHE-modified rich-split carbon capture process was conducted based on the maximum stripped gas treatment amount at a fixed membrane area. Technical and economic feasibilities of the Multi-CMHE modification were thus confirmed. The maximum net profit reaches to USD$ 2.73/t-CO2 when the regeneration heat saving is 900 kJ/kg-CO2. Sensitivity analyses indicated that this modified process is preferred in a high fuel price scenario. Additionally, the further membrane innovation should be oriented to improve the heat recovery performance and maximize the net profit in the future.

Локалізація ексергетичних втрат в утилізаторі теплоти відхідних газів газоспоживальних теплових установок

The problem of increasing the thermodynamic efficiency of power plants can be solved only by using a complex approach using methods based on modern methods of exergy analysis in combination with methods of heat transfer theory, theory of linear systems, structural-variant methods, multi-level optimization methods, etc. The analysis of the possibility of applying the discrete-modular principle and the corresponding complex method for analyzing the efficiency of the exhaust gases heat-recovery exchanger of a cogeneration unit heat engine is performed in the paper. The aim of the work is to analyze the localization of exergy losses, their differentiation, and the establishment of the relative contribution of various types of losses to the general exergy losses in the exhaust gases heat-recovery exchanger of a cogeneration unit heat engine. The structural features of the heat-recovery exchanger and the exergy properties that reflect the essence of exergy methods: universality and additivity, made it possible to use the discrete-modular principle and a complex method based on exergy-dissipative functions for efficiency analysis. The advantage of this method is the ability to analyze the localization of exergy losses in separate modules of the heat-recovery exchanger and to differentiate the exergy losses associated with nonequilibrium heat transfer between the heat-transfer agents and the wall, heat conduction and the movement of heat-transfer agents. Using the chosen complex method, the analysis of the localization of exergy losses in the heat-recovery exchanger was carried out and the exergy-dissipative functions of each of the eight modules of the heat-recovery exchanger were calculated. Differentiation of exergy losses was carried out and the relative contribution of exergy losses associated with the processes of heat transfer from flue gases to the wall, from wall to water, in heat conduction processes, as well as exergy losses associated with the movement of heat-transfer agents, in the general exergy losses was analyzed. To determine the exergy losses due to nonequilibrium heat transfer between the heat-transfer agents and the motion of the heat-transfer agents, the differential exergy equations, the equations for the heat flow densities between the heat-transfer agents and the wall, the equation for the heat flow density due to heat conduction through the wall and the equations of motion are used. It has been established that the localization of maximum exergy losses in all modules of the heat-recovery exchanger is associated with losses due to heat transfer from flue gases to the wall.

Waste heat recovery through cascaded thermal energy storage system from a diesel engine exhaust gas

One-third of heat generated is dissipated through the engine exhaust gas. Latent heat storage is one of the most efficient ways of storing thermal energy. Thermal storage units that utilise latent heat storage materials/phase change materials have received greater attention in the recent years because of their higher storage density with a smaller temperature difference between storing and releasing heat. In the present work, a heat recovery heat exchanger integrated with an IC engine and a cascade thermal energy storage systems with phase change materials, as the latent heat material is designed, fabricated and investigated. The performance characteristics of the system are also studied in detail. It is found that about 15% of fuel power is stored in the cascaded thermal energy storage system, which is available at higher and lower temperatures and it can be used for suitable applications.

Experimental investigation on innovatory waste heat recovery system impacts on DIESEL engine exhaust emissions

ABSTRACT Globally compression ignition engines are one of the major pollutants that fuel the environmental imbalance through exhaust emissions. So, this article explores the impact of innovative waste heat recovery from diesel engine harmful exhaust emissions. A double pipe, externally internally protracted finned counter flow heat exchanger (PFCHE) was innovatively planned, partially coated and tested with binary mixtures as working fluids to harvest the engine exhaust heat. The PFCHE employed, resulted in considerable amount of reduction in the emissions from engine which can be attributed to partial coating of γ-alumina diesel oxidation catalyst. The experimental result showed that there is a decline in the emissions of nitrogen oxides, carbon monoxide and hydrocarbons with partially coated PFCHE. The investigation confirmed the reduction of hydrocarbons and NOx emissions up to16% and 7% respectively at full load conditions, when compared with standard engine operations, excluding heat exchanger. There was a decrement in smoke from 60HSU to 40HSU at the time of full load engine operation. According to the results achieved from the current study, it can be inferred that the partially coated PFCHE could be an optimum heat exchanger for exhaust heat energy recovery as well as it can reduce the emissions from engine exhaust.

4E analyses of an innovative polygeneration system based on SOFC

An innovative multigeneration plant driven by a solid oxide fuel cell unit is regarded in this meticulous examination. The plausibility of the expressed plant is substantiated with regarding economic, thermodynamic and environmental concepts as the utmost efficacious equipment for operating evaluation of the thermal systems. An ejector refrigeration system beside a PEM electrolyzer are employed for cooling and hydrogen production. Furthermore, a heat recovery heat exchanger is employed for heating purposes. All subsystems are cautiously investigated and validated considering the reliable reports. The findings portrayed that the introduced multigeneration system can generate cooling load, heating capacity, net output power, and H21 rate of 84.421kW, 2771kW, 184.21kW, and 1.4331kg/h, respectively. In this occasion, the first-law efficiency, exergetic efficiency, product overall cost, and environmental penalty cost are calculated 79.57%, 33.92%, 897.7$/GJ, and 0.3527$/h, respectively. Also, among all constituents, the superior portion of exergy destruction attributed to the solid oxide fuel cell module by 783.31kW, approximately 35.6% of the overall exergy destruction rate. Meantime, a thoroughgoing parametric evaluation of the set-up is established and it is illustrated that the suggested multigeneration plant’s exergetic efficiency can be maximized according to the inlet temperature of the solid oxide fuel cell unit, compression ratio, and solid oxide fuel cell current density. Moreover, the product cost rate of the plant can be minimized with ejector motive fluid pressure, solid oxide fuel cell inlet temperature, and gas turbine outlet pressure.

Thermal efficiency evaluation for multisection heat exchange equipment in heat power installations

Comprehensive approach to improving heat exchangers for heat recovery and utilization of heat power installations is achieved by applying a step-by-step heat exchange process to be implemented in multi-section heat exchange equipment. Determination of its optimal structural, design and layout parameters can be carried out taking into account various criteria, including the use of the thermal efficiency function. Expressions for the thermal efficiency function of the objects under study are obtained in the form of complex, non-uniform heat exchange systems, on the basis of which the method for evaluating their execution options is developed. Optimal sequences of heat exchange sections, heat load distribution and operating modes for this equipment are determined.

Performance improvement of supercritical carbon dioxide power cycles through its integration with bottoming heat recovery cycles and advanced heat exchanger design: A review

In this article, the performance improvement of supercritical carbon dioxide (sCO2) Brayton cycles through heat recovery and advanced heat exchanger (HX) design is reviewed. The configuration of sCO2 cycles and the bottleneck of the design of an efficient sCO2 cycle is first evaluated. It was found that heat rejected in the precooler is a large waste that could potentially enhance the overall sCO2 system performance. Then integration of the absorption cycle, organic Rankine cycle, and thermal desalination plant to the sCO2 cycle to recover the waste thermal energy is reviewed and discussed. Results showed that these bottoming heat recovery cycles could substantially improve the overall sCO2 system efficiency. The combined system of sCO2/absorption chiller, sCO2/ORC increases the cycle efficiency to about 78% and 79%, respectively. Also, a combined system of sCO2/desalination produces about 200 000 m3/day with a cost of less than $1.0/m3. Based on the review, the evaluation criteria are proposed for decision‐makers. Another bottleneck of the design of the sCO2 system is the HXs (recuperators) used in the sCO2 cycle which are relatively large and negatively affect the cycle compactness and performance. Therefore, various types of recuperators proposed and designed for sCO2 cycles are reviewed and evaluated. This review highlights the need for further research to enhance heat recovery, reduce the cost of bottoming cycles, and improve the design of HXs.

Performance evaluation of metal-foam baffle exhaust heat exchanger for waste heat recovery

In this study, a novel metal-foam baffle cut shell and tube heat exchanger for waste heat recovery system is presented to recover heat in the exhaust gas. A 3D numerical model is established to investigate the thermal-hydraulic performance of the metal-foam baffle heat exchangers. First, the non-baffle shell and tube heat exchangers and traditional metal baffle shell and tube heat exchangers are simulated as reference for comparison. Then, the velocity distribution, temperature distribution and pressure distribution of three different types of heat exchangers are analyzed. Afterwards, the influences of exhaust gas mass flow rate and baffle thickness on pressure drop and heat transfer performance of metal-foam baffle heat exchangers and traditional ones are evaluated. The results show that, compared with traditional metal baffle heat exchangers, all metal-foam baffle exchangers show better comprehensive performance, and the area goodness factor of metal-foam baffle heat exchangers increases by 151.89%−583.62%. Among the given heat exchangers, the metal-foam baffle heat exchanger with selected metal-foam sample (MF 40.9132) is the optimum one for waste heat recovery.