scholarly journals INVESTIGATION OF THERMAL PERFORMANCE OF AIR TO WATER HEAT EXCHANGER USING NANO-FLUIDS

2011 ◽  
Vol 12 (3) ◽  
Author(s):  
Nawaf Hazim Saeid
Keyword(s):  
Heat Exchanger ◽  
Volume Fraction ◽  
Effective Properties ◽  
Three Dimensional ◽  
Cross Flow ◽  
Nano Particles ◽  
Enhancement Of Heat Transfer ◽  
Nano Powder ◽  
Flow Heat ◽  
Nano Fluids

In the present study the three-dimensional numerical simulation is selected as a tool to investigate the effectiveness of a cross flow heat exchanger. Water is selected to be mixed with nano-particles and flow inside a circular pipe while a pure air is flowing across it. Numerical simulations is carried out under laminar flow for both water and air sides. The thickness of the pipe is neglected in the present preliminary study. From the physics of the problem, the governing parameters can be determined as: the Reynolds, the type and the volume fraction of the nono-fluid. The effect of these governing parameters is studied and the results are presented. The results show significant enhancement of heat transfer with introduction of nano-particles, such as titanium-oxide (TiO2) nano-powder, compared to the pure base fluid. The accuracy of the results presented in the present study depends on the accuracy of the effective properties of the nano-fluids, which are taken from the open literature. ABSTRAK: Dalam kajian ini, simulasi tiga dimensi berangka digunakan untuk mengkaji keberkesanan penukar haba aliran silang.  Air dipilih untuk dicampurkan dengan zarah bersaiz nano dan dialirkan di dalam paip berbentuk bulat, sementara udara tulen mengalir melaluinya.  Simulasi berangka dijalankan di bawah aliran lamina untuk kedua-dua belah air dan udara. Ketebalan paip diabaikan di dalam kajian permulaan ini.  Dari sudut permasalahan fizik, parameter pengawal imbang boleh ditentukan sebagai: nombor Reynolds, jenis dan isipadu pecahan bendalir nano. Kesan parameter pengawal imbang ini dikaji dan keputusannya dibentangkan.  Keputusan menunjukkan peningkatan pemindahan haba yang ketara dengan penggunaan zarah bersaiz nano seperti serbuk titanium oksida (TiO2), berbanding dengan bendalir tulen.  Ketepatan keputusan kajian ini bergantung kepada ketepatan sifat-sifat efektif bendalir nano yang dirujuk daripada sumber maklumat terdahulu.

scholarly journals Thermal-strength analysis of a cross-flow heat exchanger and its design improvement

2021 ◽  
Vol 11 (1) ◽  
pp. 1069-1075
Author(s):  
Mariusz Konieczny ◽  
Łukasz Felkowski
Keyword(s):  
Finite Element ◽  
Heat Exchanger ◽  
Stress Concentration ◽  
Three Dimensional ◽  
Cross Flow ◽  
Element Model ◽  
Strength Analysis ◽  
Three Dimensional Model ◽  
Element Analysis ◽  
Flow Heat

Abstract After a year of the heat exchanger operation in overload conditions, a number of cracks on the tube connections to the tubesheet have been observed. To explain the stress concentration and crack initiation, a finite element analysis is performed. A three-dimensional model is constructed and analyzed. To calculate more precisely the state of stress in the most loaded regions, a submodel is created. The maximum stress exceeds the allowable stress, and according to the standards, it can lead to ratcheting. To reduce stress concentration, all tubes should be shortened and corrugated tubes are installed in the high-temperature region from the side of the burner. A finite element model of the modified heat exchanger and a submodel are created. In the modified heat exchanger, ratcheting should not occur according to the applied standards. During the operation of the modified heat exchanger, there are no further problems with cracking.

Heat and Mass Transfer to Air in a Cross Flow Heat Exchanger with Surface Deluge Cooling

2016 ◽  
Vol 24 (01) ◽  
pp. 1650002 ◽  
Author(s):  
Andrea Diani ◽  
Luisa Rossetto ◽  
Roberto Dall’Olio ◽  
Daniele De Zen ◽  
Filippo Masetto
Keyword(s):  
Heat Exchanger ◽  
Heat Flow ◽  
Flow Rate ◽  
Data Center ◽  
Heat Dissipation ◽  
Cross Flow ◽  
Critical Conditions ◽  
Heat Flow Rate ◽  
External Temperature ◽  
Flow Heat

Cross flow heat exchangers, when applied to cool data center rooms, use external air (process air) to cool the air stream coming from the data center room (primary air). However, an air–air heat exchanger is not enough to cope with extreme high heat loads in critical conditions (high external temperature). Therefore, water can be sprayed in the process air to increase the heat dissipation capability (wet mode). Water evaporates, and the heat flow rate is transferred to the process air as sensible and latent heat. This paper proposes an analytical approach to predict the behavior of a cross flow heat exchanger in wet mode. The theoretical results are then compared to experimental tests carried out on a real machine in wet mode conditions. Comparisons are given in terms of calculated versus experimental heat flow rate and evaporated water mass flow rate, showing a good match between theoretical and experimental values.

Minimum Irreversibility Criteria for Heat Exchanger Configurations

1999 ◽  
Vol 121 (4) ◽  
pp. 241-246 ◽  
Author(s):  
F. E. M. Saboya ◽  
C. E. S. M. da Costa
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Mass Flow Rates ◽  
Flow Heat

From the second law of thermodynamics, the concepts of irreversibility, entropy generation, and availability are applied to counterflow, parallel-flow, and cross-flow heat exchangers. In the case of the Cross-flow configuration, there are four types of heat exchangers: I) both fluids unmixed, 2) both fluids mixed, 3) fluid of maximum heat capacity rate mixed and the other unmixed, 4) fluid of minimum heat capacity rate mixed and the other unmixed. In the analysis, the heat exchangers are assumed to have a negligible pressure drop irreversibility. The Counterflow heat exchanger is compared with the other five heat exchanger types and the comparison will indicate which one has the minimum irreversibility rate. In this comparison, only the exit temperatures and the heat transfer rates of the heat exchangers are different. The other conditions (inlet temperatures, mass flow rates, number of transfer units) and the working fluids are the same in the heat exchangers.

Exact Solution to the Governing PDE of a Hot Water-to-Air Finned Tube Cross-Flow Heat Exchanger

2004 ◽  
Vol 10 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Chris Delnero ◽  
Dave Dreisigmeyer ◽  
Douglas Hittle ◽  
Peter Young ◽  
Charles Anderson ◽  
...  
Keyword(s):  
Exact Solution ◽  
Heat Exchanger ◽  
Cross Flow ◽  
Finned Tube ◽  
Hot Water ◽  
Flow Heat
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