scholarly journals Comparative Study of the Heat and Mass Transfer Characteristics between Counter-Flow and Cross-Flow Heat Source Towers

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2674 ◽  
Author(s):  
Yifei Lv ◽  
Jun Lu ◽  
Yongcai Li ◽  
Ling Xie ◽  
Lulu Yang ◽  
...  
Keyword(s):  
Heat Source ◽  
Cross Flow ◽  
Ambient Air ◽  
Packing Material ◽  
Operating Conditions ◽  
Solution Temperature ◽  
Low Grade ◽  
Counter Flow ◽  
Heat Pump Unit ◽  
The Impact

The heat source tower (HST), as a cleaner energy production, which can absorb the low-grade energy from ambient air to drive the heat pump unit without emissions has attracted more and more interest. In addition, HST has excellent economic applicability by using cooling tower equipment, which was idle in winter. However, there are few studies on comparative analysis of thermal behavior between counter-flow and cross-flow HST. A mathematical model suitable for both HST types was developed to identify the performance discrepancies between them. Then a parametric study was carried out in order to investigate the impact of solution and air as well as packing material properties on energy transfer of HSTs. Finally, the characteristics of solution dilution and dehumidification were investigated. As the inlet solution temperature increases, increases first, then decreases gradually, but a transition point occurs in the solution at −5 °C. Moreover, the transition section of moisture transfer direction for counter-flow HST was located in the 0.78 m and 0.26–1.56 m of packing material height, under the condition that the air relative humidity was 50%. In summary, this work intuitively indicates the thermal performance difference between counter-flow and cross-flow HST, also could assist the selection of proper operating conditions in HSTs.

The Study of Heat Consumption Systems of Buildings with Heat Pump

2016 ◽  
Vol 856 ◽  
pp. 297-302 ◽  
Author(s):  
Anna Tsynaeva ◽  
Katerina Tsynaeva
Keyword(s):  
Heat Source ◽  
Heat Pump ◽  
Heating System ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Heat Consumption ◽  
Low Grade ◽  
Consumption System ◽  
Low Grade Heat

Systems of heat consumption of the building with heat pump that uses low-grade heat source are investigated. Effectiveness of heat consumption systems with heat pump is concluded effective for severe climatic conditions prevailing in Russia. Characteristics of heat consumption system with heat pump and the traditional heating system are compared. In this case the heat pump is used the warmth of the environment, that is why considered operating conditions for the autumn and spring. Low inertia of heat systems with heat pump compared to traditional ones during autumn and spring proved.

Modeling and Analysis of Tier 4 Locomotives Operating in a High-Altitude Tunnel

2017 ◽  
Author(s):  
Kevin S. McElhaney ◽  
Robert Mischler
Keyword(s):  
High Altitude ◽  
Diesel Engines ◽  
Ambient Air ◽  
Operating Conditions ◽  
Tier 2 ◽  
Electric Locomotive ◽  
Design Changes ◽  
Engine Design ◽  
The Impact ◽  
Cooling And Lubrication

Tunnels represent one of the most severe operating conditions for diesel engines in diesel-electric locomotive applications, specifically for non-ventilated tunnels located at high elevation. High ambient air temperatures are observed in these tunnels due to heat rejected from the locomotive engines through the exhaust and engine cooling and lubrication systems. Engine protection algorithms cause the maximum allowable engine horsepower to be reduced due to these conditions leading to a reduction in train speed and occasionally train stall. A first law based model was developed to simulate the performance of a train pulled by GE diesel-electric locomotives equipped with medium speed diesel engines in a high altitude and non-ventilated tunnel. The model was compared against and calibrated to actual tunnel operation data of EPA Tier 2 compliant locomotives. The model was then used to study the impact of engine design changes required for EPA Tier 4 compliant locomotives, specifically the introduction of exhaust gas recirculation (EGR), on engine, locomotive, and train performance in the tunnel. Simulations were completed to evaluate engine control strategies targeting same or better train performance than the EPA Tier 2 compliant locomotive baseline case. Simulation results show that the introduction of EGR reduces train performance in the tunnel by increasing the required reduction in engine horsepower, but is slightly offset by improved performance from other engine design changes. The targeted engine and train performance could be obtained by disabling EGR during tunnel operation.

scholarly journals Heat Pump Use in Rural District Heating Networks in Estonia

2021 ◽  
Vol 25 (1) ◽  
pp. 786-802
Author(s):  
Kertu Lepiksaar ◽  
Kiur Kalme ◽  
Andres Siirde ◽  
Anna Volkova
Keyword(s):  
Heat Pump ◽  
Renewable Energy Sources ◽  
District Heating ◽  
Ambient Air ◽  
Heat Pumps ◽  
Hot Water ◽  
Rural District ◽  
Low Grade ◽  
The Impact ◽  
Heating Networks

Abstract District heating has proven to be an efficient way of providing space heating and domestic hot water in populated areas. It has also proven to be an excellent way to integrate various renewable energy sources (RES) into the energy system. In Estonia, biomass covers most of the heat demand, but carbon-intensive fuels are still used to cover peaks and lows. Heat pumps can be a good solution for rural areas, as there is usually plenty of land available for heat pump facilities. In addition, heat pumps require low-grade heat sources such as ambient air, groundwater, lakes, rivers, sea, sewage water, and industrial waste heat. One of the downsides of heat pumps is the need for large investments compared to boilers fired by natural gas and biomass, and electric boilers. This study examines the impact of heat pump use on consumer prices for district heating in rural district heating networks in Estonia.

Testing of a Microchannel Partial Condenser and Phase Separator in Reduced Gravity

2003 ◽  
Author(s):  
Ward E. TeGrotenhuis ◽  
Victoria S. Stenkamp
Keyword(s):  
Phase Separation ◽  
Water Pressure ◽  
Cross Flow ◽  
Ambient Air ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Reduced Gravity ◽  
Transfer Coefficients ◽  
Operation Phase ◽  
Phase Separator

Heat exchange has been successfully integrated with microchannel phase separation concepts to produce devices capable of simultaneous partial condensation and phase separation in reduced gravity. An air-cooled microchannel condenser has been tested on NASA’s KC-135 reduced gravity aircraft. The condenser was fed a mixture of air and water vapor at 70–95°C, which was cooled to below 40°C thereby generating water condensate. The condensate was successfully collected and removed as a separate stream over a range of operating conditions, thereby achieving simultaneous condensation and phase separation. Ambient air was used to cool in cross-flow with inches of water pressure drop. The microchannel device is presented along with an explanation of the principles of operation. Phase separation effectiveness and heat exchanger performance are reported for reduced gravity testing. Heat fluxes, effectiveness, and overall heat transfer coefficients are reported.

scholarly journals Influence of undefined modes of movement on instantaneous redistribution of normal reactions of quarry dump truck tires

2021 ◽  
Vol 315 ◽  
pp. 03014
Author(s):  
Mikhail Dadonov ◽  
Alexander Kulpin ◽  
Evdokia Kulpina ◽  
Valery Borovtsov ◽  
Gulzira Mukasheva
Keyword(s):  
Normal Load ◽  
Ambient Air ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Dump Truck ◽  
The Road ◽  
Truck Tires ◽  
Non Linear ◽  
Main Thing ◽  
The Impact

Reducing the costs of rock transportation in mining is one of the most important tasks. One of the reserves for solving this issue is a more complete use of the service life of quarry dump trucks tires, since their operation takes place in heavy mining and climatic conditions and this significantly reduces the life of tires. The life of tires depends on many factors: speed of movement, compliance with the recommended air pressure in the tire, ambient air temperature, but the main thing is the change in the normal load on the wheel, which depends on the redistribution of the quarry dump truck weight in case of non-linear movement and on the longitudinal profile of the quarry road. In real conditions, the quarry dump truck moves unevenly due to the complexity of the road - either braking or acceleration occur. This article allows you to evaluate the impact of non-linear modes of quarry dump truck movement on the instant redistribution of normal tire reactions and take into account peak loads on wheels during acceleration and braking in the regular cycle. This will allow you to control the load on the tires directly by cargo amount in the quarry dump truck and thereby increase the life of the tires and their reliability, as well as reduce the cost of transporting the rock mass in real operating conditions.

scholarly journals Experimental Evaluation of the Thermal Polarization in Direct Contact Membrane Distillation Using Electrospun Nanofiber Membranes Doped With Molecular Probes

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 638 ◽  
Author(s):  
Sergio Santoro ◽  
Ivan Vidorreta ◽  
Isabel Coelhoso ◽  
Joao Lima ◽  
Giovanni Desiderio ◽  
...  
Keyword(s):  
Experimental Evaluation ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Low Grade ◽  
Electrospun Nanofiber ◽  
Direct Contact Membrane Distillation ◽  
Thermal Polarization ◽  
Nanofiber Membranes ◽  
The Impact

Membrane distillation (MD) has recently gained considerable attention as a valid process for the production of fresh-water due to its ability to exploit low grade waste heat for operation and to ensure a nearly feed concentration-independent production of high-purity distillate. Limitations have been related to polarization phenomena negatively affecting the thermal efficiency of the process and, as a consequence, its productivity. Several theoretical models have been developed to predict the impact of the operating conditions of the process on the thermal polarization, but there is a lack of experimental validation. In this study, electrospun nanofiber membranes (ENMs) made of Poly(vinylidene fluoride) (PVDF) and doped with (1, 10-phenanthroline) ruthenium (II) Ru(phen)3 were tested at different operating conditions (i.e., temperature and velocity of the feed) in direct contact membrane distillation (DCMD). The temperature sensitive luminophore, Ru(phen)3, allowed the on-line and non-invasive mapping of the temperature at the membrane surface during the process and the experimental evaluation of the effect of the temperature and velocity of the feed on the thermal polarization.

scholarly journals CFD Modeling Analysis of Mechanical Draft Cooling Tower

2008 ◽  
Author(s):  
Si Y. Lee ◽  
James S. Bollinger ◽  
Alfred J. Garrett ◽  
Larry D. Koffman
Keyword(s):  
Water Droplet ◽  
Cooling Tower ◽  
Waste Heat ◽  
National Laboratory ◽  
Ambient Air ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Test Results ◽  
Savannah River ◽  
The Impact

Industrial processes use mechanical draft cooling towers (MDCT’s) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional momentum, energy, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was benchmarked against the literature data and the SRS test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed modeling and test results will be presented here.

Modeling and Analysis of Tier 4 Locomotives Operating in a High-Altitude Tunnel

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Kevin S. McElhaney ◽  
Robert Mischler
Keyword(s):  
High Altitude ◽  
Diesel Engines ◽  
Ambient Air ◽  
Operating Conditions ◽  
Tier 2 ◽  
Electric Locomotive ◽  
Design Changes ◽  
Engine Design ◽  
The Impact ◽  
Cooling And Lubrication

Tunnels represent one of the most severe operating conditions for diesel engines in diesel-electric locomotive applications, specifically for nonventilated tunnels located at high elevation. High ambient air temperatures are observed in these tunnels due to heat rejected from the locomotive engines through the exhaust and engine cooling and lubrication systems. Engine protection algorithms cause the maximum allowable engine horsepower to be reduced due to these conditions leading to a reduction in train speed and occasionally train stall. A first law based model was developed to simulate the performance of a train pulled by GE diesel-electric locomotives equipped with medium speed diesel engines in a high altitude and nonventilated tunnel. The model was compared against and calibrated to actual tunnel operation data of EPA Tier 2 compliant locomotives. The model was then used to study the impact of engine design changes required for EPA Tier 4 compliant locomotives, specifically the introduction of exhaust gas recirculation (EGR), on engine, locomotive, and train performance in the tunnel. Simulations were completed to evaluate engine control strategies targeting same or better train performance than the EPA Tier 2 compliant locomotive baseline case. Simulation results show that the introduction of EGR reduces train performance in the tunnel by increasing the required reduction in engine horsepower, but is slightly offset by improved performance from other engine design changes. The targeted engine and train performance could be obtained by disabling EGR during tunnel operation.

scholarly journals One-Dimensional Modelling of a Trilateral Flash Cycle System with Two-Phase Twin-Screw Expanders for Industrial Low-Grade Heat to Power Conversion

Designs ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 41 ◽  
Author(s):  
Giuseppe Bianchi ◽  
Matteo Marchionni ◽  
Stuart Kennedy ◽  
Jeremy Miller ◽  
Savvas Tassou
Keyword(s):  
Power Conversion ◽  
Operating Conditions ◽  
Staggered Grid ◽  
Inlet Temperature ◽  
Low Grade ◽  
Two Phase ◽  
One Dimensional ◽  
Twin Screw ◽  
Low Grade Heat ◽  
The Impact

This paper provides an overview of a one-dimensional modelling methodology for equipment and systems for heat to power conversion based on a staggered grid space discretization and implemented in the commercial software GT-SUITE®. Particular attention is given to a newly developed modelling procedure for twin-screw machines that is based on a chamber modelling approach and considers leakage paths between cells and with the casing. This methodology is then applied to a low-grade heat to power conversion system based on a Trilateral Flash Cycle (TFC) equipped with two parallel two-phase twin-screw expanders and a control valve upstream of the machines to adapt the fluid quality for an optimal expander operation. The standalone expander model is used to generate performance maps of the machine, which serve as inputs for the TFC system model. Parametric analyses are eventually carried out to assess the impact of several operating parameters of the TFC unit on the recovered power and cycle thermal efficiency. The study shows that the most influencing factors on the TFC system’s performance are the inlet temperature of the heat source and the expander speed. While the first depends on the topping industrial process, the expander speed can be used to optimize and control the TFC system operation also in transient or off-design operating conditions.

Experimental Investigation of a LiCl-Water Open Absorption System for Cooling and Dehumidification

2004 ◽  
Vol 126 (2) ◽  
pp. 710-715 ◽  
Author(s):  
K. Gommed ◽  
G. Grossman ◽  
F. Ziegler
Keyword(s):  
Air Conditioning ◽  
Experimental System ◽  
Ambient Air ◽  
Operating Conditions ◽  
Low Grade ◽  
Laboratory System ◽  
Transfer Coefficients ◽  
Theoretical Investigations ◽  
Absorption Cycle ◽  
Low Grade Heat

In earlier work, a novel open absorption cycle was proposed, capable of producing both cooling and dehumidification for air conditioning, utilizing low-grade heat. The system, referred to as DER (Dehumidifier-Evaporator-Regenerator), uses ambient air in conjunction with an absorbent solution; the air is dehumidified and then employed to produce chilled water in an evaporative cooler. Alternatively, a portion of the dehumidified air may be used directly for air conditioning purposes. The system thus has the potential to provide both cooling and dehumidification in variable ratios, as required by the load. Computer simulations and theoretical investigations were carried out to analyze and predict the performance of the system. The objective of the present study has been to construct a laboratory system to test the concept, identify problems and carry out preliminary design optimization. The characteristic performance of individual components, analyzed theoretically in the simulation, was studied experimentally. Measurements have provided much-needed realistic data about heat and mass transfer coefficients. The performance of the system has been studied under varying operating conditions. The paper describes the operation of the experimental system and presents the measured data and the resulting transfer coefficients.

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