scholarly journals The Optimization of the Thermal Performances of an Earth to Air Heat Exchanger for an Air Conditioning System: A Numerical Study

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6414
Author(s):  
Adriana Greco ◽  
Claudia Masselli
Keyword(s):  
Heat Exchanger ◽  
Numerical Study ◽  
Geothermal System ◽  
Inlet Temperature ◽  
Burial Depth ◽  
Pipe Length ◽  
Air Conditioning System ◽  
Air Inlet ◽  
System A ◽  
The City

The aim of this paper is to research the parameters that optimize the thermal performances of a horizontal single-duct Earth to Air Heat eXchanger (EAHX). In this analysis, the EAHX is intended to be installed in the city of Naples (Italy). The study is conducted by varying the most crucial parameters influencing the heat exchange between the air flowing in the duct and the ground. The effect of the geometrical characteristics of the duct (pipe length, diameter, burial depth), and the thermal and flow parameter of humid air (inlet temperature and velocity) has been studied in order to optimize the operation of this geothermal system. The results reveal that the thermal performance increases with length until the saturation distance is reached. Moreover, if the pipe is designed with smaller diameters and slower air flows, if other conditions remain equal, the outlet temperatures come closer to the ground temperature. The combination that optimizes the performance of the system, carried out by forcing the EAHX with the design conditions for cooling and heating, is: D = 0.1 m s−1; v = 1.5 m s−1; L = 50 m. This solution could also be extended to horizontal multi-tube EAHX systems.

scholarly journals Numerical analysis on heat transfer and flow resistance performances of a heat exchanger with novel perforated wavy fins

2021 ◽  
pp. 255-255
Author(s):  
Xuexi Wang ◽  
Feng Lin
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Wave Amplitude ◽  
Numerical Study ◽  
Inlet Temperature ◽  
S Wave ◽  
Air Inlet ◽  
Good Agreement

In this paper, the experimental and numerical study of thermo-hydraulic characteristics of perforated wavy fin heat exchanger and unperforated wavy fin heat exchanger were conducted. Firstly, the two kinds of fins were studied under different air inlet velocity and constant inlet temperature. The results show that Nusselt number increases with Reynolds number and friction factor decreases with Reynolds number. Then, the performance of the two kinds of fins is numerically analyzed, and the simulation results are in good agreement with the experimental data. On this basis, the influence of different perforated fin parameters (fin height H, fin pitch s, wave amplitude wa, perforation number n, perforation diameter d) on the thermal performance of wavy fin heat exchanger is discussed. It is indicated that friction factor and Nusselt number increase with increasing aperture, wave amplitude, fin pitch and perforation number or decreasing fin height under constant Reynolds number condition. Finally, the performance evaluation of heat exchangers with different parameters is carried out to obtain the best performance heat exchanger parameters, which can provide a reference for the design of the new wavy fin heat exchanger.

Application of Artificial Neural Networks to Predict Heat Transfer From Buried Pipe for Ground Source Heat Pump Applications

2013 ◽  
Author(s):  
Hakan Demir ◽  
Ş. Özgür Atayılmaz ◽  
Özden Agra ◽  
Ahmet Selim Dalkılıç
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Energy Resource ◽  
Heat Pumps ◽  
Burial Depth ◽  
Buried Pipe ◽  
Ground Source Heat Pumps ◽  
Ground Source ◽  
Artificial Neural

The earth is an energy resource which has more suitable and stable temperatures than air. Ground Source Heat Pumps (GSHPs) were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. Design of GSHP systems in different regions of US and Europe is performed using data from an experimental model. However, there are many more techniques including some complex calculations for sizing GHEs. An experimental study was carried out to investigate heat transfer in soil. A three-layer network is used for predicting heat transfer from a buried pipe. Measured fluid inlet temperatures were used in the artificial neural network model and the fluid outlet temperatures were obtained. The number of the neurons in the hidden layer was determined by a trial and error process together with cross-validation of the experimental data taken from literature evaluating the performance of the network and standard sensitivity analysis. Also, the results of the trained network were compared with the numerical study.

scholarly journals Air-side performance of a micro-channel heat exchanger in wet surface conditions

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 375-385 ◽  
Author(s):  
Raviwat Srisomba ◽  
Lazarus Asirvatham ◽  
Omid Mahian ◽  
Ahmet Dalkılıç ◽  
Mohamed Awad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Relative Humidity ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Micro Channel ◽  
Surface Conditions ◽  
Air Inlet ◽  
Wet Surface

The effects of operating conditions on the air-side heat transfer, and pressure drop of a micro-channel heat exchanger under wet surface conditions were studied experimentally. The test section was an aluminum micro-channel heat exchanger, consisting of a multi-louvered fin and multi-port mini-channels. Experiments were conducted to study the effects of inlet relative humidity, air frontal velocity, air inlet temperature, and refrigerant temperature on air-side performance. The experimental data were analyzed using the mean enthalpy difference method. The test run was performed at relative air humidities ranging between 45% and 80%; air inlet temperature ranges of 27, 30, and 33?C; refrigerant-saturated temperatures ranging from 18 to 22?C; and Reynolds numbers between 128 and 166. The results show that the inlet relative humidity, air inlet temperature, and the refrigerant temperature had significant effects on heat transfer performance and air-side pressure drop. The heat transfer coefficient and pressure drop for the micro-channel heat exchanger under wet surface conditions are proposed in terms of the Colburn j factor and Fanning f factor.

scholarly journals Numerical Study and Experimental Validation of Skim Milk Drying in a Process Intensified Counter Flow Spray Dryer

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4974
Author(s):  
Umair Jamil Ur Rahman ◽  
Artur K. Pozarlik
Keyword(s):  
Feed Rate ◽  
Numerical Study ◽  
Skim Milk ◽  
Product Recovery ◽  
Lagrangian Model ◽  
Average Error ◽  
Inlet Temperature ◽  
Counter Flow ◽  
Two Phase ◽  
Air Inlet

This research presents 3D steady-state simulations of a skim milk spray drying process in a counter-current configuration dryer. A two-phase flow involving gas and discrete phase is modeled using the Eulerian–Lagrangian model with two-way coupling between phases. The drying kinetics of skim milk is incorporated using the Reaction Engineering Approach. The model predictions are found to be in accordance with the experimental temperature measurements with a maximum average error of 5%. The validated computational model is employed further to study the effects of nozzle position, initial spray Sauter Mean Diameter (SMD), air inlet temperature, and feed rate on the temperature and moisture profiles, particle impact positions, drying histories, and product recovery at the outlet. The location of the nozzle upwards (≈23 cm) resulted in maximum product recovery and increased the mean particle residence time at the outlet. A similar trend was observed for the highest feed rate of 26 kg/h owing to the increased spray penetration upstream in the chamber. The maximum evaporation zone was detected close to the atomizer (0–10 cm) when the spray SMD is 38 µm, whereas it shifts upstream (40–50 cm) of the dryer for an SMD of 58 µm. The high air inlet temperature resulted in enhanced evaporation rates only in the initial 10–20 cm distance from the atomizer. The results obtained in this study are beneficial for the development of the novel vortex chamber-based reactors with a counter flow mechanism.

A Numerical Investigation on the Performance of an Earth Air Heat Exchanger System for the Indian District of Nagpur

2014 ◽  
Vol 592-594 ◽  
pp. 1398-1402
Author(s):  
Rohit Tripathy ◽  
Sadhana Mishra ◽  
R. Thundil Karuppa Raj
Keyword(s):  
Heat Exchanger ◽  
Flow Distribution ◽  
Soil Conditions ◽  
Internal Diameter ◽  
Inlet Temperature ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Pipe Length ◽  
Using Data ◽  
Energy Equations

The performance of an Earth-Air Heat Exchanger (EAHE) system to be operated in climatic and soil conditions prevailing in the Indian district of Nagpur is modeled numerically. To do so, a CFD model is developed in ANSYS Fluent 12.1. The validation of the CFD model is carried out using data obtained from published literature and good agreement is established between the simulation results and published experimental data. An earth pipe of length 60 m and internal diameter 0.1 m is chosen for validating the model and this validated model is used to further investigate for three different lengths of the pipe - 40 m, 35 m and 30 m. The 3-dimensional flow field through the earth air heat exchanger is studied numerically by solving the appropriate governing equations namely: continuity, momentum and energy equations and a finite volume CFD code is employed for solving the same. An air inlet velocity of 2 m/s is maintained and the inlet temperature was varied between 308.1 K and 315 K for each chosen length. The decrease in temperature and flow distribution along the pipe length is plotted.

A Numerical Study of the Effect of Inlet Vent Position and Size on the Velocity and Temperature Distributions in a Smaller Naturally Ventilated Theater in Canada

2014 ◽  
Author(s):  
Patrick H. Oosthuizen
Keyword(s):  
Indoor Air ◽  
Natural Ventilation ◽  
Numerical Study ◽  
Uniform Heat Flux ◽  
Ansys Fluent ◽  
Air Conditioning System ◽  
Discharge System ◽  
System A ◽  
Side Walls ◽  
Air Discharge

Many smaller churches and similar buildings in Canada have been converted into small theaters. Such theatres are often not fitted with an air-conditioning system. For performances in the fall these theaters sometimes rely on buoyancy driven natural ventilation to moderate the indoor air temperature. Such ventilation systems usually involve near floor inlet vents and a roof level air discharge system. A preliminary numerical study of the effect of inlet vent position and size on the performance of such a system has been undertaken. A simple model of a typical theater building of the type considered has been used. The heat generated by the audience has been represented by a uniform heat flux distributed over the audience area. Inlet vents have been assumed to be located low on the side walls of the theater and the air-flow leaving the theatre has been assumed to be through vents at the top of a chimney system. The flow has been assumed to be steady and symmetrical about the vertical center-line through the building. The Boussinesq approach has been adopted. The standard k-epsilon turbulence model has been used. The solution has been obtained using the commercial CFD solver ANSYS FLUENT©.

Numerical Simulation of Oscillating Heat Pipe Heat Exchanger

2010 ◽  
Vol 6 (1) ◽  
Author(s):  
Benyin Chai ◽  
Min Shao ◽  
Xuanyou Li ◽  
Shenjie Zhou ◽  
Yongchun Shi
Keyword(s):  
Numerical Simulation ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Pipe ◽  
High Efficiency ◽  
Inlet Temperature ◽  
Oscillating Heat Pipe ◽  
Air Inlet ◽  
Hot Air ◽  
Pipe Heat

Oscillating heat pipe is a new type high efficiency heat-transfer element. Its development and design attract increasing attention. This paper describes a numerical simulation for investigating on the flow and heat exchange performance of an oscillating heat pipe heat exchanger. The influences of the arrangement of heat pipe, the inlet temperature and the flux of hot air were explored. The results show that the heat exchange of staggered arrangement is more efficient than the aligned one. The influence of temperature difference on the heat exchanger by hot air flux is more than hot air inlet temperature.

scholarly journals Multi-stage heat-pipe heat exchanger for improving energy efficiency of the HVAC system in a hospital operating room 1

2020 ◽  
Author(s):  
Ragil Sukarno ◽  
Nandy Putra ◽  
Imansyah Ibnu Hakim ◽  
Fadhil Fuad Rachman ◽  
Teuku Meurah Indra Mahlia
Keyword(s):  
Heat Exchanger ◽  
Air Conditioning ◽  
Energy Recovery ◽  
Heat Recovery ◽  
Heat Pipes ◽  
Inlet Temperature ◽  
Hvac System ◽  
Inlet Velocity ◽  
Air Inlet ◽  
Pipe Heat

Abstract The demands of specific requirements related to thermal comforts, such as temperature, relative humidity, inside air exchange and other factors required in a hospital operating rooms, have necessitated the development of energy-efficient heating, ventilation and air conditioning (HVAC) systems and efficient heat-recovery system using a heat-pipe heat exchanger (HPHE). The experiment was conducted by using HPHEs having three, six and nine rows, with four heat pipes in each row, arranged in a staggered configuration with a variation of fresh-air inlet temperature and velocity. The theoretical analysis was conducted using the ε-NTU method for predicting the effectiveness, outlet temperature of the evaporator side and energy recovery of the HPHE. The experimental results indicated that increasing the air-inlet temperature in the evaporator section and the number of rows increased the HPHE effectiveness but increasing the air-inlet velocity reduced the effectiveness. The highest effectiveness of 62.6% was obtained at an air-inlet temperature of 45°C with an air-inlet velocity of 2 m/s and a 9-row HPHE. The energy recovery of the HPHE increased with the number of rows, air-inlet temperature and air velocity in the evaporator section. The ε-NTU method can be used as a comparison method in the analysis of heat-recovery systems that apply HPHE air conditioning systems. Heat pipes that utilize cold-air exhaust from a room in an HVAC system can enhance efficiency and reduce emissions.

scholarly journals Numerical Study of a Helical Heat Exchanger for Wort Cooling in the Artisanal Beer Production Process

2020 ◽  
Vol 29 (54) ◽  
pp. e11632
Author(s):  
Fernando Toapanta-Ramos ◽  
Luis González-Rojas ◽  
Elmo Calero ◽  
Bryan Calderón ◽  
William Quitiaquez
Keyword(s):  
Heat Exchanger ◽  
Cold Water ◽  
Numerical Study ◽  
Computational Techniques ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Ansys Fluent ◽  
Craft Beer ◽  
Helical Heat Exchanger ◽  
Beer Production

The objective of the present work is to study the behavior of a helical tube and shell heat exchanger, for the cooling of the wort in the process of making craft beer with cold water, through the methodology of computational fluid dynamics (CFD) by finite volume models for heat exchanger modeling. This by using the ANSYS Fluent software, which allows to understand the behavior of the fluid through equations that describe their movement and behavior, using numerical methods and computational techniques. In the mesh convergence, two methods were used, orthogonality and obliquity, with which it was confirmed that the meshing is ideal in the simulations that were carried out. For the simulation, the k-epsilon turbulence model and the energy model were used. Through various simulations, it was obtained that by varying the mass flow, better results are reducing the outlet temperature, with a variation of 15.16 °C, while varying the inlet temperature of the water, there is just a variation from 2.71 °C to 0.01 °C. Therefore, a significant improvement in the performance of the heat exchanger was found. In the same way, it was confirmed that the number of spikes in the heat exchanger is adequate, since the outlet temperature would not be reached with less spikes.

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