scholarly journals ANALYSIS OF ENERGY CONSUMPTION ECONOMY IN CRYOGENIC SYSTEMS BY THE USE OF HEAT EXCHANGERS

2017 ◽  
Vol 60 (3) ◽  
pp. 256-264
Author(s):  
A. V. Trotsenko
Keyword(s):  
Energy Consumption ◽  
Heat Exchanger ◽  
Power Consumption ◽  
Heat Exchangers ◽  
Power Plants ◽  
Operating Regime ◽  
Working Fluid ◽  
Mode Of Operation ◽  
Required Quality ◽  
Power Costs

Evaluation of energy consumption economy due to implementation of the principle of cold regeneration is a formidable problem of exergy analysis of cryogenic systems. A method or evaluation of power consumption economy due to the presence of heat exchangers in the scheme of cryogenic plant is suggested in the present article. The calculations of the economy for the refrigeration and liquefaction regimes of cryogenic nitrogen plant operating in accordance with a simple throttle cycle have been carried out. The approximate method for evaluation of power consumption economy demonstrated that for a simple throttle cycle the use of the heat exchanger enables to reduce power costs by about 30 % regardless of the mode of operation. The use of a heat exchanger makes it possible to avoid the problems associated with the use of work produced in the expander. The analysis of the results of the performed calculations demonstrated that the economy is practically independent on the operating regime. For the analyzed systems the minimal pressures of the working fluid after compressor that are needed to obtain a specified quantity of a product of required quality have been determined. The calculations made for Linde cycle demonstrated that this value depends on the mode of operation, but it is significantly less than the pressure in the cycle. The presented approach to determining the economy of energy consumption in low-temperature systems is applicable to power plants due to the presence of heat exchangers in its design. For such an application one need to override the purpose of these devices and to alter the equations exergy balances in accordance with it.

scholarly journals Investigation of heat transfer enhancement in an annular conduit with angled fins using functionalized GNP colloidal suspension

2021 ◽  
Vol 945 (1) ◽  
pp. 012058
Author(s):  
Sayshar Ram Nair ◽  
Cheen Sean Oon ◽  
Ming Kwang Tan ◽  
S.N. Kazi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Colloidal Suspension ◽  
Industrial Applications ◽  
Point Of View ◽  
Solid Particles ◽  
Working Fluid

Abstract Heat exchangers are important equipment with various industrial applications such as power plants, HVAC industry and chemical industries. Various fluids that are used as working fluid in the heat exchangers such as water, oil, and ethylene glycol. Researchers have conducted various studies and investigations to improve the heat exchanger be it from material or heat transfer point of view. There have been attempts to create mixtures with solid particles suspended. This invention had some drawbacks since the pressure drop was compromised, on top of the occurrence of sedimentation or even erosion, which incurs higher maintenance costs. A new class of colloidal suspension fluid that met the demands and characteristics of a heat exchanger was then created. This novel colloidal suspension mixture was then and now addressed as “nanofluid”. In this study, the usage of functionalized graphene nanoplatelet (GNP) nanofluids will be studied for its thermal conductivity within an annular conduit with angled fins, which encourage swirling flows. The simulation results for the chosen GNP nanofluid concentrations have shown an enhancement in thermal conductivity and heat transfer coefficient compared to the corresponding base fluid thermal properties. The data from this research is useful in industrial applications which involve heat exchangers with finned tubes.

scholarly journals Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2737
Author(s):  
Francesca Ceglia ◽  
Adriano Macaluso ◽  
Elisa Marrasso ◽  
Maurizio Sasso ◽  
Laura Vanoli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Heat Transfer Area ◽  
Geothermal Fluid ◽  
Shell And Tube

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants using organic fluids for electricity “production” or in cogeneration configuration. The improvement in the use of geothermal aquifers at low-medium enthalpy in small deep sites favours the reduction of drilling well costs, and in addition, it allows the exploitation of local resources in the energy districts. The heat exchanger evaporator enables the thermal heat exchange between the working fluid (which is commonly an organic fluid for an Organic Rankine Cycle) and the geothermal fluid (supplied by the aquifer). Thus, it has to be realised taking into account the thermodynamic proprieties and chemical composition of the geothermal field. The geothermal fluid is typically very aggressive, and it leads to the corrosion of steel traditionally used in the heat exchangers. This paper analyses the possibility of using plastic material in the constructions of the evaporator installed in an Organic Rankine Cycle plant in order to overcome the problems of corrosion and the increase of heat exchanger thermal resistance due to the fouling effect. A comparison among heat exchangers made of commonly used materials, such as carbon, steel, and titanium, with alternative polymeric materials has been carried out. This analysis has been built in a mathematical approach using the correlation referred to in the literature about heat transfer in single-phase and two-phase fluids in a tube and/or in the shell side. The outcomes provide the heat transfer area for the shell and tube heat exchanger with a fixed thermal power size. The results have demonstrated that the plastic evaporator shows an increase of 47.0% of the heat transfer area but an economic installation cost saving of 48.0% over the titanium evaporator.

THE EFFECT OF LIQUID SUCTION HEAT EXCHANGER SUB-COOLER ON PERFORMANCE OF A FREEZER USING R404A AS WORKING FLUID

2015 ◽  
Vol 76 (11) ◽  
Author(s):  
Muhammad Nuriyadi ◽  
Sumeru Sumeru ◽  
Henry Nasution
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cooling Capacity ◽  
Experimental Results ◽  
Working Fluid ◽  
Liquid Line ◽  
Cabin Temperature

This study presents the effect of liquid-suction heat exchangers (LSHX) sub-cooler in a freezer. The LSHX sub-cooler is a method to increase the cooling capacity of the evaporator by lowering temperature at the condenser outlet. The decrease in temperature of the condenser outlet will cause a decrease in the quality refrigerant entering the evaporator. The lower the quality of the refrigerant entering the evaporator, the higher the cooling capacity produced by the evaporator. The LSHX sub-cooler utilizes a heat exchanger to transfer heat from the outlet of the condenser (liquid line) to the suction of the compressor. In the present study, three different LSHX sub-coolers in the freezer with cabin temperature settings of 0, -10 and -20oC were investigated. The results showed that the lowest and the highest of effectiveness of the heat exchanger were 0.28 and 0.58, respectively. The experimental results also showed that EER reduction is occurred at the cabin temperature setting of 0oC and -10oC, whereas the EER improvements were always occurred at the cabin temperature settings of -20oC.

scholarly journals Yearly Cost Saving by Using Enthalpy Heat Exchanger During Cooling and Heating

2020 ◽  
Vol 328 ◽  
pp. 01014
Author(s):  
Kamil Križo ◽  
Andrej Kapjor ◽  
Martin Vantúch
Keyword(s):  
Energy Consumption ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Building Energy ◽  
Sensible Heat ◽  
Oxygen Level ◽  
Optimal Temperature ◽  
Air Handling Unit ◽  
Save Energy ◽  
Yearly Cost

Fresh air has to be constantly supplied to the building by air handling unit, where supplied air is mixed with inside air and optimal temperature, oxygen level is adjusted and level of dust and smoke is reduced. Supply air demand of the building is determined according to number of persons in the room, room area and regulations. Necessity of ventilation rely in supplying room with oxygen, cleaning the air, adjusting temperature and moisture and reduction of odours, gases, dust, bacteria and viruses. Achieving optimal properties of supply air creates huge portion of building energy consumption. To save energy during ventilation, standard air to air sensible heat exchangers are used. They purpose is to recover sensible heat from exhaust air and at the same time avoid contamination of supply air. Drawback of these types of exchangers is limit of recovering moisture, therefore huge portion of energy in form of latent heat is lost. On top of classical plate air to air heat exchanger, enthalpy heat exchanger allows to exchange latent as well as sensible heat [1].

scholarly journals OTEC Maximum Net Power Output Using Carnot Cycle and Application to Simplify Heat Exchanger Selection

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1143 ◽  
Author(s):  
Kevin Fontaine ◽  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Power Output ◽  
Heat Exchangers ◽  
Power Plants ◽  
Seawater Temperature ◽  
Carnot Cycle ◽  
Ocean Thermal Energy ◽  
Net Power Output

Ocean thermal energy conversion (OTEC) uses the natural thermal gradient in the sea. It has been investigated to make it competitive with conventional power plants, as it has huge potential and can produce energy steadily throughout the year. This has been done mostly by focusing on improving cycle performances or central elements of OTEC, such as heat exchangers. It is difficult to choose a suitable heat exchanger for OTEC with the separate evaluations of the heat transfer coefficient and pressure drop that are usually found in the literature. Accordingly, this paper presents a method to evaluate heat exchangers for OTEC. On the basis of finite-time thermodynamics, the maximum net power output for different heat exchangers using both heat transfer performance and pressure drop was assessed and compared. This method was successfully applied to three heat exchangers. The most suitable heat exchanger was found to lead to a maximum net power output 158% higher than the output of the least suitable heat exchanger. For a difference of 3.7% in the net power output, a difference of 22% in the Reynolds numbers was found. Therefore, those numbers also play a significant role in the choice of heat exchangers as they affect the pumping power required for seawater flowing. A sensitivity analysis showed that seawater temperature does not affect the choice of heat exchangers, even though the net power output was found to decrease by up to 10% with every temperature difference drop of 1 °C.

Novel Evaporator Geometries Based on Entrance-Length Flow-Paths for Geothermal Binary Power Plants

2016 ◽  
Author(s):  
Adrian S. Sabau ◽  
Ali H. Nejad ◽  
James W. Klett ◽  
Adrian Bejan ◽  
Kivanc Ekici
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Cost Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Length Scale ◽  
Entrance Length ◽  
Scale Levels

In this paper, a novel geometry is proposed for evaporators that are used in Organic Rankine Cycles. The proposed geometry consists of employing successive plenums at several length-scale levels, creating a multi-scale heat exchanger. The channels at the lowest length-scale levels were considered to have their length given by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to obtain performance indicators for new heat exchangers and baseline heat exchangers. The relationship between the size of the channels at one level, k, with respect to the size of the channels at the next level, k + 1, is based on generalization of the “Murray’s law.” In order to account for the variation of the temperature and heat transfer coefficient in the entrance region, a heat transfer model was developed. The variation of the brine and refrigerant temperatures along each pipe was considered. Using the data on pumping power and weight of metal structures, including that of all the plenums and piping, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. In addition to the total present cost, the data on overall thermal resistance is also used in identifying optimal heat exchanger configurations. The main design variables include: tube arrangement, number of channels fed from plenum, and number of rows in the tube bank seen by the outside fluid. In order to assess the potential improvement of the new evaporator designs, baseline evaporators were designed. The baseline evaporator designs include long tubes of the same diameter as those of the lowest length-scale levels, placed between one inlet and one outlet. The baseline evaporator designs were created from the new evaporator designs by simply removing most of the internal plenums employing tubes much longer than their entrance length, as they would currently be used. Consistent with geothermal applications, the performance of new heat exchanger designs was compared to that of baseline heat exchanger designs at the same flow rates. For some operating conditions it was found that the new heat exchangers outperform their corresponding baseline heat exchangers.

scholarly journals Energy Consumption for Acceleration of the Upper Parts of Plants in the Interval between the Belt of the Upper Conveyor and the Deck

2020 ◽  
pp. 76-79
Author(s):  
В.А. Николаев ◽  
В.В. Гумённый
Keyword(s):  
Energy Consumption ◽  
Power Consumption ◽  
Technological Process ◽  
Angular Acceleration ◽  
Animal Husbandry ◽  
Energy Costs ◽  
Design Version ◽  
Grinding Method ◽  
Combine Harvesters ◽  
Required Quality

Задачей любого технологического процесса является выполнение заданной работы с необходимым качеством и наименьшими затратами энергии. При уборке зерновых культур зерноуборочными комбайнами наибольшие затраты энергии связаны с выделением зёрен из колосьев. Это обусловлено необходимостью протаскивания соломы через молотильное устройство. Чтобы выделить зёрна из колосьев методом вытирания, необходимо срезать только верхние части растений. Оставшиеся стебли соломы следует измельчать и, в зависимости от технологии, либо рассеивать по полю, либо погружать в транспортные средства для использования в животноводстве. Существуют два варианта исполнения устройства для извлечения зёрен из колосьев: с декой, совершающей колебания, и с неподвижной декой. Извлечение зёрен из колосьев методом вытирания, когда дека неподвижна, является энергетически более целесообразным в сравнении с вариантом конструктивного исполнения комбайна, у которого дека совершает колебания. После попадания верхней части растения в промежуток между лентой верхнего транспортёра и декой происходит её линейное и угловое ускорение. Как на линейное, так и на угловое ускорение верхней части растения расходуется энергия. В результате расчётов определена энергия, необходимая для ускорения верхних частей растений, расположенных на деке, и потребляемая мощность. The task of any technological process is to perform the specified work with the required quality and the lowest energy consumption. When harvesting grain crops with combine harvesters, the greatest energy costs are associated with the extract of grains from ears. This is due to the need to pull straw through the threshing device. To extract grains from ears by grinding, it is necessary to cut only the upper parts of plants. The remaining straw stems should be ground and depending on the technology either scattered across the field or loaded in vehicles for use in animal husbandry. There are two versions of the device for extracting grains from ears: with a deck making vibrations, and with a fixed deck. The extraction of grains from the ears by the grinding method when the deck is stationary is energetically more expedient compared to the design version of the combine in which the deck oscillates. After the upper part of the plant enters the gap between the belt of the upper conveyor and the deck its linear and angular acceleration occurs. Both linear and angular acceleration of the upper part of the plant consumes energy. As a result of the calculations, the energy necessary to accelerate the upper parts of plants located on the deck and the power consumption were determined.

scholarly journals Study on Shell-and-Tube Heat Exchanger Models with Different Degree of Complexity for Process Simulation and Control Design

2018 ◽  
Author(s):  
Javier Bonilla
Keyword(s):  
Heat Exchanger ◽  
Molten Salt ◽  
Heat Exchangers ◽  
Control Strategies ◽  
Thermal Storage ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Test Loop ◽  
Shell And Tube ◽  
Thermal Oil

Many commercial solar thermal power plants rely on indirect thermal storage systems in order to provide a stable and reliable power supply, where the working fluid is commonly thermal oil and the storage fluid is molten salt. The thermal oil - molten salt heat exchanger control strategies, to charge and discharge the thermal storage system, strongly affect the performance of the whole plant. Shell-and-tube heat exchangers are the most common type of heat exchangers used in these facilities. With the aim of developing advanced control strategies accurate and fast dynamic models of shell-and-tube heat exchangers are essential. For this reason, several shell-and-tube heat exchanger models with different degrees of complexity have been studied, analyzed and validated against experimental data from the CIEMAT-PSA molten salt test loop for thermal energy systems facility. Simulation results are compared in steady-state as well as transient predictions in order to determine the required complexity of the model to yield accurate results.

Industrial Technical Development and Qualification of Highly Efficient Stainless Steel Plates and Fins Heat Exchanger for Heat Removal Supercritical CO2 Brayton Cycle Applied to Nuclear Power Plants

2020 ◽  
Author(s):  
Sarah Tioual-Demange ◽  
Gaëtan Bergin ◽  
Thierry Mazet ◽  
Luc de Camas
Keyword(s):  
Stainless Steel ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Supercritical Co2 ◽  
Nuclear Power ◽  
Power Plants ◽  
Heat Removal ◽  
Eutectic Phase ◽  
Steel Plates ◽  
Brayton Cycle

Abstract The sCO2-4-NPP european project aims to develop an innovative technology based on supercritical CO2 (sCO2) for heat removal to improve the safety of current and future nuclear power plants. The heat removal from the reactor core will be achieved with multiple highly compact self-propellant, self-launching, and self-sustaining cooling system modules, powered by a sCO2 Brayton cycle. Heat exchangers are one of the key components required for advanced Brayton cycles using supercritical CO2. Fives Cryo company, a brazed plates and fins heat exchangers manufacturer, with its expertise in thermal and hydraulic design and brazing fabrication is developing compact, and highly efficient stainless steel heat exchanger solution for sCO2 power cycles, thanks to their heat exchange capability with low pinch and high available flow sections. The aim of the development of this specific heat exchanger technology is to achieve an elevated degree of regeneration. For this matter, plates and fins heat exchanger is a very interesting solution to meet the desired thermal duty with low pressure drop leading to a reduction in size and capital cost. The enhancement of the mechanical integrity of plates and fins heat exchanger equipment would lead to compete with, and even outweigh, printed circuit heat exchangers technology, classically used for sCO2 Brayton cycles. sCO2 cycle conditions expose heat exchangers to severe conditions. Base material selection is essential, and for cost reasons, it is important to keep affordable heat-resistant austenitic stainless steel grades, much cheaper than a nickel-based alloy. Another advantage of high compactness of plates and fins heat exchangers is the diminution of the amount of material used in the heat exchanger manufacturing, decreasing even more its cost. The challenge here is to qualify stainless steel plates and fins heat exchangers mechanical resistance, at cycle operating conditions, and meet with pressure vessels codes and regulations according to nuclear requirements. One critical point in the development of the heat exchangers is the design of the fins. As secondary surface, they allow the maximization of heat transfer at low pressure drop. At the same time mechanical strength has to be guaranteed. To withstand high pressure, fins thickness has to be significant, which makes the implementation complicated. Efforts were dedicated to successfully obtain an optimal shape. Forming of fins was therefore improved compared to conventional techniques. Important work was undertaken to define industrial settings to flatten the top of the fins leading to a maximum contact between the brazing alloy and the fins. Consequently brazed joints quantity is minimized inducing a diminution of the presence of eutectic phase, which is structurally brittle and limits the mechanical strength of the construction. A metallurgical study brings other elements leading to the prevention of premature rupture of the brazed structure. The idea is to determine an optimized solidification path and to identify a temperature range and holding time where the brazed joint is almost free of eutectic phase during the assembly process in the vacuum furnace.

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