Hamid Nalbandian | National Central University (original) (raw)

Hamid Nalbandian

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Papers by Hamid Nalbandian

Research paper thumbnail of Condensation heat transfer of HFO-1234yf and HFC-134a in small tube

8th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2016, 2016

Research paper thumbnail of Flow Boiling Heat Transfer of Refrigerants HFO-1234yf and HFC-134a in an Extruded Aluminum Tube with Multi-Port microchannels

International Journal of Refrigeration

Research paper thumbnail of An experimental investigation on flow boiling heat transfer of refrigerants HFO-1234yf and HFC-134a in microchannels

Highlights  The heat transfer coefficient is measured using R-600a.  The effect of mass velocit... more Highlights  The heat transfer coefficient is measured using R-600a.  The effect of mass velocity, heat flux and quality conditions is investigated.  The influence of flow patterns on the heat transfer coefficient is observed.  Heat transfer coefficient results are compared to several predicted correlations.

Research paper thumbnail of Condensation heat transfer and pressure drop of refrigerants HFO-1234yf and HFC-134a in small circular tube

International Journal of Heat and Mass Transfer

A class of delayed ratio-dependent Gause-type predator-prey model is considered. Firstly, the eig... more A class of delayed ratio-dependent Gause-type predator-prey model is considered. Firstly, the eigenvalue problem is studyed for the linearized system at the coexisting equilibrium and a group of sufficient conditions for the existence of Hopf bifurcation are obtained. Secondly, the direction of the Hopf bifurcation and the stability of the bifurcated periodic solutions are determined by applying the normal form method and the center manifold theorem. Finally, some numerical simulations are carried out to illustrate the obtained results.

Research paper thumbnail of Flow boiling heat transfer and pressure drop of refrigerants HFO-1234yf and HFC-134a in small circular tube

International Journal of Heat and Mass Transfer, 2018

Research paper thumbnail of A FLOW PATTERN BASED COMPARISON ON TWO-PHASE PRESSURE DROPS OF REFRIGERANTS HFO-1234 yf AND HFC-134 a IN MICROCHANNEL HEAT EXCHANGER

Owing to the global warming effect consideration, the EU has banned the use of refrigerants with ... more Owing to the global warming effect consideration, the EU has banned the use of refrigerants with Global Warming Potential (GWP) value higher than 150 in all new passenger cars starting from 1 January 2017 (EU directive 2006/40/EC [1]. The study on the replacement of high GWP refrigerant such as HFC-134a has become an important and urgent issue. Recently, a new refrigerant, HFO-1234yf has been developed with similar thermodynamic properties to HFC-134a but much lower GWP value (GWP = 4 in comparing to 1,430 of HFC-134a). It is expected as a good candidate of replacing the refrigerant HFC-134a. However, most of the heat transfer and flow performances are still not very clear up-to-date. For reducing the weight of heat exchangers, most of the vehicles air-condition systems used extruded aluminum tubes in their evaporators and condensers. The hydraulic diameter of the heat exchangers is generally very small, which called microchannel heat exchanger, to resist the high working pressure o...

Research paper thumbnail of Effect of channel size and shape on condensation heat transfer of refrigerants HFO-1234yf and HFC-134a in rectangular microchannels

International Journal of Heat and Mass Transfer

Research paper thumbnail of Applying the CHP method on small-scale on-site power generation

2013 IEEE Conference on Clean Energy and Technology (CEAT), 2013

ABSTRACT Considering the increasing rate of energy consumption, dramatic lack of energy sources a... more ABSTRACT Considering the increasing rate of energy consumption, dramatic lack of energy sources and approaching energy crises in the world the increase in the efficiency of electrical appliances and using renewable energy has recently become indisputable part of new technologies. Consequently, in this article an attempt will be made to introduce a new and simple method to increase the efficiency of On-site Distributed generators through CHP (combined heat and power) techniques and the result of using this method will be compared to SHP(single heat and power) techniques in the field of efficiency and environment. As it will be shown, employing this method will exert significant influences on the efficiency of generators.

Research paper thumbnail of Condensation heat transfer of HFO-1234yf and HFC-134a in small tube

8th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2016, 2016

Research paper thumbnail of Flow Boiling Heat Transfer of Refrigerants HFO-1234yf and HFC-134a in an Extruded Aluminum Tube with Multi-Port microchannels

International Journal of Refrigeration

Research paper thumbnail of An experimental investigation on flow boiling heat transfer of refrigerants HFO-1234yf and HFC-134a in microchannels

Highlights  The heat transfer coefficient is measured using R-600a.  The effect of mass velocit... more Highlights  The heat transfer coefficient is measured using R-600a.  The effect of mass velocity, heat flux and quality conditions is investigated.  The influence of flow patterns on the heat transfer coefficient is observed.  Heat transfer coefficient results are compared to several predicted correlations.

Research paper thumbnail of Condensation heat transfer and pressure drop of refrigerants HFO-1234yf and HFC-134a in small circular tube

International Journal of Heat and Mass Transfer

A class of delayed ratio-dependent Gause-type predator-prey model is considered. Firstly, the eig... more A class of delayed ratio-dependent Gause-type predator-prey model is considered. Firstly, the eigenvalue problem is studyed for the linearized system at the coexisting equilibrium and a group of sufficient conditions for the existence of Hopf bifurcation are obtained. Secondly, the direction of the Hopf bifurcation and the stability of the bifurcated periodic solutions are determined by applying the normal form method and the center manifold theorem. Finally, some numerical simulations are carried out to illustrate the obtained results.

Research paper thumbnail of Flow boiling heat transfer and pressure drop of refrigerants HFO-1234yf and HFC-134a in small circular tube

International Journal of Heat and Mass Transfer, 2018

Research paper thumbnail of A FLOW PATTERN BASED COMPARISON ON TWO-PHASE PRESSURE DROPS OF REFRIGERANTS HFO-1234 yf AND HFC-134 a IN MICROCHANNEL HEAT EXCHANGER

Owing to the global warming effect consideration, the EU has banned the use of refrigerants with ... more Owing to the global warming effect consideration, the EU has banned the use of refrigerants with Global Warming Potential (GWP) value higher than 150 in all new passenger cars starting from 1 January 2017 (EU directive 2006/40/EC [1]. The study on the replacement of high GWP refrigerant such as HFC-134a has become an important and urgent issue. Recently, a new refrigerant, HFO-1234yf has been developed with similar thermodynamic properties to HFC-134a but much lower GWP value (GWP = 4 in comparing to 1,430 of HFC-134a). It is expected as a good candidate of replacing the refrigerant HFC-134a. However, most of the heat transfer and flow performances are still not very clear up-to-date. For reducing the weight of heat exchangers, most of the vehicles air-condition systems used extruded aluminum tubes in their evaporators and condensers. The hydraulic diameter of the heat exchangers is generally very small, which called microchannel heat exchanger, to resist the high working pressure o...

Research paper thumbnail of Effect of channel size and shape on condensation heat transfer of refrigerants HFO-1234yf and HFC-134a in rectangular microchannels

International Journal of Heat and Mass Transfer

Research paper thumbnail of Applying the CHP method on small-scale on-site power generation

2013 IEEE Conference on Clean Energy and Technology (CEAT), 2013

ABSTRACT Considering the increasing rate of energy consumption, dramatic lack of energy sources a... more ABSTRACT Considering the increasing rate of energy consumption, dramatic lack of energy sources and approaching energy crises in the world the increase in the efficiency of electrical appliances and using renewable energy has recently become indisputable part of new technologies. Consequently, in this article an attempt will be made to introduce a new and simple method to increase the efficiency of On-site Distributed generators through CHP (combined heat and power) techniques and the result of using this method will be compared to SHP(single heat and power) techniques in the field of efficiency and environment. As it will be shown, employing this method will exert significant influences on the efficiency of generators.

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