scholarly journals Thermo-Economic Analysis of a Hybrid Ejector Refrigerating System Based on a Low Grade Heat Source

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 562 ◽  
Author(s):  
Gianluca Lillo ◽  
Rita Mastrullo ◽  
Alfonso William Mauro ◽  
Raniero Trinchieri ◽  
Luca Viscito
Keyword(s):  
Heat Transfer ◽  
Economic Analysis ◽  
Energy Demand ◽  
Alternative Energy ◽  
Waste Heat ◽  
Plant Size ◽  
Low Grade ◽  
Two Phase ◽  
Pinch Point ◽  
Cost Of Energy

The rising of the global energy demand requires the use of alternative energy conversion systems employing renewable sources. In the refrigeration and air conditioning fields, heat driven ejector systems represent a promising way to produce the cooling effect by using available low-grade temperature sources. In this paper, a thermo-economic analysis of a waste heat recovery hybrid ejector cycle (WHRHEC) was carried out. A thermodynamic model was firstly developed to simulate a WHRHEC able to obtain chilled water with a cooling load of 20 kW, by varying the working fluids and the pinch point values in the heat exchangers. Specific single- and two-phase heat transfer correlations were used to estimate the heat transfer surface and therefore the investment costs. The operative ranges that provide a reasonable compromise between the set-up costs and the cycle performances were then defined and compared to the current waste heat-driven technologies, such as absorption chillers and organic Rankine cycles (ORCs) coupled with vapor compression cycles (VCCs). The last part of the paper presents an economic analysis providing the map of the design (plant size) and contingent (specific cost of energy, waste heat availability) variables that lead to the economic convenience of a WHRHEC system when integrated to a conventional VCC plant.

Integration of Low-Grade Heat from Exhaust Gases into Energy System of the Enterprise

2021 ◽  
Author(s):  
Petro Kapustenko ◽  
Olga Arsenyeva ◽  
Olena Fedorenko ◽  
Sergiy Kusakov
Keyword(s):  
Heat Exchanger ◽  
Process Integration ◽  
Waste Heat ◽  
Gaseous Mixture ◽  
Energy System ◽  
Low Grade ◽  
Two Phase ◽  
Pinch Point ◽  
Exhaust Gases ◽  
Composite Curve

Abstract In the paper is presented the way of Process Integration application for waste heat utilisation from exhaust gases streams with partial condensation. It is based on the construction of Hot Composite Curve representing the gaseous mixture cooling with accounting for the gas-liquid equilibrium of condensable vapour part. With Cold Composite Curve for streams requiring heating, the Pinch Point is determined. Then the structure of Heat Exchanger Network (HEN) for utilised Heat Integration into the energy system of the factory is developed accounting for the possible splitting of two-phase flow on gas and liquid streams and selection of plate heat exchanger (PHE) types for specific positions in HEN. The method is illustrated by a case study of heat utilisation from exhaust gases after superheated steam tobacco drying and flue gases from natural gas-fired boiler. The heat transfer areas of PHEs in HEN are optimised with the total annualised cost as an objective function. The payback period of the received solution is less than four months with a substantial saving of energy, reduction of greenhouse gases and other harmful emissions of combustion processes.

Meanline Analysis and CFD Study of a Radial Inflow Turbine With Vaneless Distributor for Low Temperature Organic Rankine Cycle

2020 ◽  
Author(s):  
M. Deligant ◽  
S. Braccio ◽  
T. Capurso ◽  
F. Fornarelli ◽  
M. Torresi ◽  
...  
Keyword(s):  
Energy Demand ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Low Grade ◽  
Heat Sources ◽  
Turbine Wheel ◽  
Good Efficiency ◽  
Low Grade Heat

Abstract The Organic Rankine Cycle (ORC) allows the conversion of low-grade heat sources into electricity. Although this technology is not new, the increase in energy demand and the need to reduce CO2 emissions create new opportunities to harvest low grade heat sources such as waste heat. Radial turbines have a simple construction, they are robust and they are not very sensitive to geometry inaccuracies. Most of the radial inflow turbines used for ORC application feature a vaned nozzle ensuring the appropriate distribution angle at the rotor inlet. In this work, no nozzle is considered but only the vaneless gap (distributor). This configuration, without any vaned nozzle, is supposed to be more flexible under varying operating conditions with respect to fixed vanes and to maintain a good efficiency at off-design. This paper presents a performance analysis carried out by means of two approaches: a combination of meanline loss models enhanced with real gas fluid properties and 3D CFD computations, taking into account the entire turbomachine including the scroll housing, the vaneless gap, the turbine wheel and the axial discharge pipe. A detailed analysis of the flow field through the turbomachine is carried out, both under design and off design conditions, with a particular focus on the entropy field in order to evaluate the loss distribution between the scroll housing, the vaneless gap and the turbine wheel.

Oscillating Heat Pipes for Waste Heat Recovery in HVAC Systems

2015 ◽  
Author(s):  
Govinda Mahajan ◽  
Heejin Cho ◽  
Scott M. Thompson ◽  
Harrison Rupp ◽  
Kevin Muse
Keyword(s):  
Heat Transfer ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Heat Pipes ◽  
Hvac Systems ◽  
Operating Conditions ◽  
Working Fluid ◽  
Low Grade ◽  
Potential Cost

Oscillating heat pipes (OHPs) were experimentally assessed as a passive-type heat transfer device for air-to-air heat exchange in a typical Heating Ventilation & Air conditioning system (HVAC) with adjacent air streams at different temperatures. The objective is to utilize, otherwise wasted thermal energy to pre-heat or pre-cool air in order to reduce the payload on HVAC systems, thus reducing energy consumption. OHPs can achieve effective thermal conductivities on-the-order of 10,000 W/m-K via no internal wicking structure and hence can perform aforementioned heat transfer task while providing an aerodynamic form factor. A unique working fluid with limited research inside OHPs, but with properties desirable for low grade heat fluxes, i.e. n-pentane with 70 % fill ratio, was chosen as the working fluid to achieve maximum heat transfer. Aerodynamic performance, in terms of pressure drop, was evaluated and juxtaposed with heat transfer gain/loss. The OHP thermal performance and total heat transfer for hot-environment HVAC operation was benchmarked with an empty/evacuated OHP with same overall dimensions. Results indicate that the current, atypically-long OHP is fully-capable of operating in the air-to-air convection mode for waste heat recovery for typical HVAC operating conditions. Since the OHP is passive, cost effective, and relatively aerodynamic (no fins were used), the potential cost savings for its integration into HVAC systems can be significant.

Design and Analysis of Ejector Powerplant System

2013 ◽  
Author(s):  
Menandro S. Berana ◽  
Edward T. Bermido
Keyword(s):  
High Pressure ◽  
Ambient Temperature ◽  
Waste Heat ◽  
Temperature Drop ◽  
Working Fluid ◽  
Low Grade ◽  
Heat Sources ◽  
Two Phase ◽  
Evaporator Temperature ◽  
Working Fluids

An ejector is a device with no moving components and is made up of four main parts: converging-diverging nozzle, suction chamber, mixing section and diffuser. It has become popular in refrigeration system as it gives the advantage of recovering expansion energy from high pressure difference into compression energy. In this study, the potential use of ejector in powerplants that use low-grade or low temperature heat sources was conceptualized and analytically investigated. A novel combination of the ejector and the organic Rankine cycle (ORC) was proposed. The driving fluid in the ejector of the proposed powerplant cycle is the high-pressure liquid in the separator that is just circulated back to the evaporator in the ORC. Further increase in turbine temperature drop (TTD), which can increase the power output and efficiency of the plant, can be achieved through expansion, mixing and recompression processes in the ejector. Ocean thermal energy conversion (OTEC), solar-boosted OTEC (SOTEC), solar-thermal, waste-heat driven, biomass and geothermal powerplants were considered in the analysis. Mathematical models in our previous studies were developed and used to calculate for nozzle and ejector parameters. The geometric profile of the ejector for optimization with categorized heat sources was determined. Isentropic, internally reversible, and irreversible two-phase nozzle expansions were analyzed. Two-phase flow calculations were continued in the mixing section. It was assumed that the constant-pressure mixing of the primary and secondary fluids occur at the hypothetical throat inside the constant-area section. Calculation for shock wave in the mixing section was also done. The diffuser was analyzed in a similar manner with the nozzle. Calculation for other components and plant efficiencies was finally conducted. Ammonia and propane which are both natural working fluids were used in the analysis. Evaporator temperature range from 293.15 K to 393.15 K and condenser and ambient temperatures range from 283.15 K to 308.15 K were used in the analysis. The lowest ambient temperature of 283.15 K was used for the OTEC and SOTEC powerplants. It was shown that ammonia and propane can operate up to 11 K and 12 K below the ambient temperature, respectively. Ejector efficiency ranged from 90 to 95% for both working fluids. The maximum efficiencies of the ejector powerplant were 19.2% for ammonia and 14.9% for propane, compared to 11.7% and 9.8% of the conventional ORC. It was analytically determined that the efficiency of the ejector powerplant is higher than that of the ORC powerplant for the same working fluid and conditions of the evaporator, condenser and the ambient.

scholarly journals A Framework for Design and Operation Optimization for Utilizing Low-Grade Industrial Waste Heat in District Heating and Cooling

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2190
Author(s):  
Lingwei Zhang ◽  
Yufei Wang ◽  
Xiao Feng
Keyword(s):  
Industrial Waste ◽  
Energy Demand ◽  
Heat Recovery ◽  
Waste Heat ◽  
District Heating ◽  
Mixed Integer ◽  
Low Grade ◽  
Operation Optimization ◽  
Heating And Cooling ◽  
Industrial Waste Heat

In the process industry, a large amount of low-grade waste heat is discharged into the environment. Furthermore, district heating and cooling systems require considerable low-grade energy. The integration of the two systems has great significance for energy saving. Because the energy demand of consumers varies in periods, the design and operation of an industrial waste heat recovery system need to match with the fluctuations of district energy demand. However, the impact of the periodic changes on the integration schemes are not considered enough in existing research. In this study, a framework method for solving above problem is proposed. Industrial waste heat was integrated with a district heating and cooling system through a heat recovery loop. A three-step mathematical programming method was used in design and operation optimization for multiperiod integration. A case study was conducted, and the results show that the multiperiod optimization method can bring significant benefits to the system. By solving the mixed integer nonlinear programming model, the optimal operation plans of the integration in different periods can be obtained.

scholarly journals Assessment of economic, thermal and hydraulic performances a corrugated helical heat exchanger filled with non-Newtonian nanofluid

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Ibrahim ◽  
Ebrahem A. Algehyne ◽  
Tareq Saeed ◽  
Abdallah S. Berrouk ◽  
Yu-Ming Chu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Exchanger ◽  
Economic Analysis ◽  
Evaluation Criteria ◽  
Methyl Cellulose ◽  
Hydraulic Performance ◽  
Two Phase ◽  
Heat Transfer Efficiency ◽  
Helical Heat Exchanger

AbstractImproved heat transfer efficiency with considering economic analysis in heating systems is an interesting topic for researchers and scientists in recent years. This research investigates the heat transfer rate (HTR) and flow of non-Newtonian water-Carboxyl methyl cellulose (CMC) based Al2O3 nanofluid in a helical heat exchanger equipped with common and novel turbulators using two-phase model. The requirements for dimensions and cost reduction and also energy saving in thermal systems are the main goal of this study. According to gained results usage of corrugated channel in helical heat exchanger has a considerable influence on thermal and hydraulic performance evaluation criteria (THPEC) index of helical heat exchanger and can improve the THPEC index. Thus, Re = 5000 is obtained as an optimum value, in which the maximum THPEC value is achieved. As it is found in this paper, in case of using novel heat exchanger instead of the basic smooth system, the thermal properties (by considering Nusselt number) increases about 210%, the hydraulic performance (friction factor) reduces about 28%, performance evaluation criteria index increases about 57% and the material consumption (in case of similar THPEC) decreases about 31%. In another word, with considering economic analysis for the basic and novel system which has same efficiencies, the novel one has lower length and consequently 31% lower material.

Exergo-economic analysis of finned tube for waste heat recovery including phase change heat transfer

2013 ◽  
Vol 27 (11) ◽  
pp. 3513-3523
Author(s):  
Shuang-Ying Wu ◽  
Jing-Rui Jiu ◽  
Lan Xiao ◽  
You-Rong Li ◽  
Chao Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Economic Analysis ◽  
Phase Change ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Finned Tube ◽  
Phase Change Heat Transfer

scholarly journals Entropy and Entransy Dissipation Analysis of a Basic Organic Rankine Cycles (ORCs) to Recover Low-Grade Waste Heat Using Mixture Working Fluids

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 818 ◽  
Author(s):  
Yong-qiang Feng ◽  
Qian-hao Luo ◽  
Qian Wang ◽  
Shuang Wang ◽  
Zhi-xia He ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Mass Fraction ◽  
Waste Heat ◽  
Low Grade ◽  
Outlet Temperature ◽  
Entransy Dissipation ◽  
Minimum Entropy ◽  
Pinch Point ◽  
Working Fluids ◽  
Condenser Temperature

Mixture working fluids can reduce effectively energy loss at heat sources and heat sinks, and therefore enhance the organic Rankine cycle (ORC) performance. The entropy and entransy dissipation analyses of a basic ORC system to recover low-grade waste heat using three mixture working fluids (R245fa/R227ea, R245fa/R152a and R245fa/pentane) have been investigated in this study. The basic ORC includes four components: an expander, a condenser, a pump and an evaporator. The heat source temperature is 120 °C while the condenser temperature is 20 °C. The effects of four operating parameters (evaporator outlet temperature, condenser temperature, pinch point temperature difference, degree of superheat), as well as the mass fraction, on entransy dissipation and entropy generation were examined. Results demonstrated that the entransy dissipation is insensitive to the mass fraction of R245fa. The entropy generation distributions at the evaporator for R245/pentane, R245fa/R152a and R245fa/R227ea are in ranges of 66–74%, 68–80% and 66–75%, respectively, with the corresponding entropy generation at the condenser ranges of 13–21%, 4–17% and 11–21%, respectively, while those at the expander for R245/pentane, R245fa/R152a and R245fa/R227ea are approaching 13%, 15% and 14%, respectively. The optimal mass fraction of R245fa for the minimum entropy generation is 0.6 using R245fa/R152a.

Prospects for greater efficiency in the use of different energy sources

1977 ◽  
Vol 281 (980) ◽  
pp. 261-275 ◽  
Keyword(s):  
Alternative Energy ◽  
Fossil Fuels ◽  
Crop Residues ◽  
Waste Heat ◽  
Energy Sources ◽  
Alternative Energy Sources ◽  
The United Kingdom ◽  
Cost Of Energy ◽  
Self Sufficiency ◽  
The Media

The United Kingdom grows a little more than one half of its food and it is shown that agriculture uses 4 % of national energy to make this unprocessed food available at the farm gate. Small though this may be, it is absolutely vital to British agriculture, for present levels of productivity are highly dependent on its use, principally through the media of mechanization and fertilizers. The prospects for the United Kingdom’s indigenous energy supplies are examined and it is shown that while self-sufficiency seems assured in the 1980s, before the turn of the century we may once again be competing in world markets for scarce and expensive fossil fuels. The prospects for making better use of existing and alternative energy sources in agriculture are discussed. It is shown that conservation measures may be practised in relation to existing energy sources in respect of powered machines, cultivations, drying of crops and glasshouse heating and that there are also possibilities in respect of fertilizers. New and under-used sources considered include solar energy by direct and photosynthetic means (energy crops), crop residues, animal wastes, wind power, industrial waste heat, and geothermal energy, and some examples are given of their application to agricultural systems. Some of these new and under-used sources of energy appear to offer some prospects of supplementing present sources but their future will be critically dependent on the availability and cost of energy from these more conventional sources.

scholarly journals Specifics in the operating modes of thermosyphon air heater of steam generators №1 and №2 in TPP "Republika" at fuel switch from coal to natural gas

2019 ◽  
Vol 85 ◽  
pp. 01003 ◽  
Author(s):  
Iliya Iliev ◽  
Angel Terziev ◽  
Hristo Beloev ◽  
Christiyan Iliev
Keyword(s):  
Heat Transfer ◽  
Natural Gas ◽  
Complex Geometry ◽  
Waste Heat ◽  
Numerical Study ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Operating Modes ◽  
Heat Transfer Coefficients ◽  
Harmful Emissions

A fuel switch is motivated both by the necessity of increasing energy efficiency and the compliance with the ever-stricter regulations regarding the release of harmful emissions in the environment. In this paper a thorough financial and energy analysis on the fuel switch from coal to natural gas is carried out, in particular with respect to waste heat recovery systems (two phase thermosyphons). As a result of the calculation of the heat transfer coefficients for both fuels, it is established that the system running on natural gas has a lower value, due to the lower air velocity, caused in turn by the lower requirement for excess air. The heat transfer coefficients of the evaporation and condensation zones respectively are established hfgas=104.9 И hair=84.9 (W/m2.K) for coal and hfgas И hair =84.7 (W/m2.K) respectively for gas. A numerical study is also carried out and a methodology for the analysis of the efficiency of two phase thermosyphons with complex geometry is presented.

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