effect of mass flow rate on thermohydraulic ......lo2 at constant temperature of 70k . the result...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 7, July 2017, pp. 1900–1905, Article ID: IJMET_08_07_211

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

EFFECT OF MASS FLOW RATE ON

THERMOHYDRAULIC PERFORMANCE OF

HTS CABLES WITH MIXED CRYOGEN

Priyanka Anand

Graduate Student, School of Mechanical Engineering,

Lovely Professional University, Phagwara, Punjab, India.

Gaurav Vyas

Assistant Professor, School of Mechanical Engineering,


Raja Sekhar Dondapati

Associate Professor, School of Mechanical Engineering,


Rahul Agarwal

UG Student, School of Mechanical Engineering,


ABSTRACT

The process of power transmission in conventional power cables exhibits huge

transmission losses. For better future power transmission system, a novel technique is

being developed using High Temperature Superconducting (HTS) cables. Cooling of

these cables below the critical temperature of superconductor is necessary in order to

maintain superconductivity. HgBa2Ca2Cu2O2 superconductor with highest critical

temperature of 134K has been attained which necessitate the requirement of efficient

coolant to overcome losses.

In the present work, mixture of liquid nitrogen and liquid oxygen is proposed to be

the suitable coolant. For this purpose, investigation on thermophysical properties is

carried out using SUPERTRAPP®. Also thermohydraulic performance (pressure drop

and heat transfer) is being evaluated by adopting Computational Fluid Dynamics

(CFD) analysis technique at given mass flow rates. The obtained results show

increase in pressure drop, heat transfer and Nusselt number with increase in mass

flow rate at constant temperature.

Key words: HTS cables, Liquid nitrogen (LN2) and Liquid Oxygen (LOX), Pressure

drop and Heat transfer, Nusselt number.

Effect of Mass Flow Rate on Thermohydraulic Performance of HTS Cables with Mixed Cryogen


Cite this Article: Priyanka Anand, Gaurav Vyas, Raja Sekhar Dondapati and Rahul

Agarwal Effect of Mass Flow Rate on Thermohydraulic Performance of HTS Cables

with Mixed Cryogen International Journal of Mechanical Engineering and

Technology, 8(7), 2017, pp. 1900–1905.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

1. INTRODUCTION High Temperature Superconducting cables are proved to be efficient alternative to the

conventional power transmission system. Comparatively less power losses in HTS cables help

them in power grid application [1]-[3]. Although high heat dissipation needs various cooling

techniques [4]-[6].However, these cooling techniques are not found to be excessively

beneficial, so requirement for suitable coolant for better power transmission arise. Dondapati

R.S [7] suggested Super Critical Nitrogen (SCN) to be one such coolant.

The utility of mixed cryogenic fluid can be another alternative cooling solution for HTS

cables. Jung-Bin Song [8] has also used mixed cryogen for HTS power application. However,

paper presents mixture of solid-liquid nitrogen. In this research work mixture of Liquid

Nitrogen (LN2) and Liquid Oxygen (LOX) is considered to be feasible coolant at operating

temperature of 70K and pressure range of 0.9MPa-1.3MPa. The thermophysical properties are

evaluated using NIST database standard 4 (SUPERTRAPP®) versions 3.2.1 as investigated

by Afrianto [9] for numerical study on LNG flow and heat transfer characteristic in heat

exchanger. Estimation of thermohydraulic properties of cryogens are utilized in computational

fluid dynamic analysis for performing thermohydraulic performance of High Temperature

Superconductivity Cables [10-14] Properties obtained are then simulated in CFD [10]-[11] at

varying mass flow rates. The geometry of HTS cable for the analysis is shown in figure 1.

Figure 1 Geometry of HTS cable modeled using ABAQUS [7]

2. RESEARCH METHODOLOGY

In the present research work varying composition of mixed cryogen ranging from 10-90% to

90-10% is taken with increasing liquid nitrogen and decreasing liquid oxygen percentage in

the composition. The mixture composition is considered to be 10gms. Density, viscosity,

thermal conductivity and specific heat are evaluated at operating temperature of 70K and

pressure range of 0.9MPa to 1.3MPa at varying composition of mixed cryogen.

The computational fluid geometry of corrugated steel for mixed LN2 and LOX is

developed in ANSYS (FLUENT)-15.0.0 version in the following dimensions.

Priyanka Anand, Gaurav Vyas, Raja Sekhar Dondapati and Rahul


Table 1 Dimensions for corrugated steel pipe

Pipe diameter Corrugation Pitch Length of pipe Mass flow rate

(mm) (mm) (mm) (g/s)

40 60 1000 20-60

Figure 2 Schematic of corrugated steel pipe for computational analysis

Geometry developed is meshed and solved in FLUENT with inlet condition of constant

temperature of 70K and operating pressure from 0.9MPa to 1.3MPa. The wall temperature is

taken to be 290K and no changes on outlet of the pipe are made. Conservation of mass,

conservation of momentum and conservation of energy equations are simultaneously solved at

varying mass flow rates in FLUENT from 20g/s to 60g/s. Pressure drop ,heat transfer and

Nusselt number is calculated from the obtained results for HTS cables for mixed cryogen as

conducted by Dondapati R.S [12] for long length internally cooled HTS cables. Governing

equations considered [12] for calculation of pressure drop and Nusselt Number are

∆� ��

2�

Where Δp = Pressure Drop (Pa), f = Friction Factor, L =Length of the Corrugated pipe

(m), ρ= Density of mixed cryogen (kg/m3), D = Diameter of pipe (m).

Also the Nusselt number is dimensionless number as function of temperature in fluid and

is given as

��

�

Where h=Heat Transfer coefficient (W/m2-K), k=thermal conductivity (W/m-K).

The unknown value of heat transfer coefficient is calculated

� � ��∆�



Where Q= heat transfer (W), A= area of pipe (m2), ∆�= Tinlet – Tout let (K)

The values of friction factor and heat transfer can be obtained from FLUENT post-

processing module.

3. RESULTS AND DISCUSSION In this paper, the thermohydraulic performance of mixed LN2 and LOX at specified

temperature and pressure range is evaluated using Computational Fluid Dynamics (CFD). The

analysis of pressure drop, heat transfer and Nusselt number is estimated at various mass flow

rates. The analysis is done by considering various the mass flow rates. The significant change

is recorded with varying mass flow rate. Also increase in amount of liquid nitrogen in mixed

cryogen shows maximum pressure drop, heat transfer and Nusselt number. Whereas mixed

cryogen with minimum volume of liquid oxygen records the least rise in pressure drop, heat

transfer and Nusselt number.

3.1. Pressure Drop Analysis

Figure 3 Pressure Drop as function of Mass flow Rate for various composition of mixed cryogen at

70K and a) 0.9MPa b) 1.0MPa c) 1.1MPa d) 1.2MPa e) 1.3 MPa

Figure 3 represents the pressure drop as function of mass flow rate ranging from 0.02kg/s-

0.06kg/s with mixture combination range of 10-90% to 90-10% by volume of LN2-LO2 at

constant temperature of 70K . It is observed that with increase in mass flow rate, pressure

drop increases. Likewise, with increase of LN2 in mixture significant increase in pressure

drop is marked.

Priyanka Anand, Gaurav Vyas, Raja Sekhar Dondapati and Rahul


3.2. Heat Transfer Analysis

Figure 4 Heat transfer as function of Mass Flow Rate for various composition of mixed cryogen at


Figure 4 represents the heat transfer as function of mass flow rate ranging from 0.02kg/s-

0.06kg/s with mixture combination range of 10-90% to 90-10% by volume of LN2-LO2 at

constant temperature of 70K . It is observed that with increase in mass flow rate, heat transfer

increases. Likewise, with increase of LN2 in mixture significant increase in heat transfer is

marked.

3.3. Nusselt Number Analysis

Figure 5 Nusselt number as function of Mass Flow Rate for various composition of mixed cryogen at




Figure5 represents the Nusselt number as function of mass flow rate ranging from

0.02kg/s-0.06kg/s with mixture combination range of 10-90% to 90-10% by volume of LN2-

LO2 at constant temperature of 70K . The result indicates that with increase in mass flow rate,

Nusselt number increases. Likewise, with increase of LN2 in mixture significant increase in

Nusselt number is marked.

4. CONCLUSION Pressure drop and heat transfer is investigated for the HTS cables. With the use of mixed

cryogen, a significant increase in heat transfer is marked for various mass flow rates.

Likewise, pressure drop and Nusselt number also increase as mass of mixed cryogen is

increased. Also the cryogen with maximum volume percentage of liquid nitrogen exhibits

maximum pressure drop, heat transfer and Nusselt number.

REFERENCES

[1] D. Yoon, “A feasibility study on HTS cable for the grid integration of renewable energy,”

Phys. Procedia, vol. 45, pp. 281–284, 2013.

[2] A. P. Malozemoff, J. Yuan, and C. M. Rey, 5 - High-temperature superconducting AC

cables for power grid applications. Elsevier Ltd, 2015.

[3] S. C. Wimbush, “Large scale applications of HTS in New Zealand,” Phys. Procedia, vol.

65, pp. 221–224, 2015.

[4] J. A. Demko et al., “Testing of a 1 . 5-m Single-Phase Short-Sample Cable Made With

Copper Laminated HTS Tapes at ORNL,” vol. 15, no. 2, pp. 1755–1758, 2005.

[5] R. Martin, “Cryogenic System For A High-Temperature Transmission Cable ”.

[6] L. H. T. S. Cables, J. A. Demko, and R. C. Duckworth, “Cooling Configuration Design

Considerations for,” vol. 19, no. 3, pp. 1752–1755, 2009.

[7] Dondapati, R. S., Ravula, J., Thadela, S., & Usurumarti, P. R. (2015). Analytical

approximations for thermophysical properties of supercritical nitrogen (SCN) to be used

in futuristic high temperature superconducting (HTS) cables. Physica C:

Superconductivity and Its Applications, 519, 53–59.

[8] J. Song and H. Lee, “Mixed cryogen cooling systems for HTS power applications : A

status report of progress in Korea University,” Cryogenics (Guildf)., vol. 52, no. 12, pp.

648–655, 2012.

[9] H. Afrianto, R. Tanshen, B. Munkhbayar, U. T. Suryo, H. Chung, and H. Jeong,

“International Journal of Heat and Mass Transfer A numerical investigation on LNG flow

and heat transfer characteristic in heat exchanger,” Int. J. Heat Mass Transf., vol. 68, pp.

110–118, 2014.

[10] R. S. Dondapati and V. V Rao, “Entropy generation minimization (EGM) to optimize

mass flow rate in dual channel cable-in-conduit conductors (CICCs) used for fusion grade

magnets,” Fusion Eng. Des., pp. 1–10, 2014.

[11] R. S. Dondapati, G. S. Member, and V. V Rao, “CFD Analysis of Cable-In-Conduit

Conductors ( CICC ) for Fusion Grade Magnets,” vol. 22, no. 3, 2012.

[12] R. S. Dondapati and V. V Rao, “Long Length Internally Cooled HTS Cables,” vol. 23, no.

3, pp. 2–5, 2013.

[13] D. R. Sekhar and V. V Rao, “Three dimensional CFD analysis of Cable-in-Conduit

Conductors ( CICCs ) using porous medium approach,” Cryogenics (Guildf)., vol. 54, pp.

20–29, 2013.

[14] R. S. Dondapati and V. V Rao, “Influence of mass flow rate on Turbulent Kinetic Energy

(TKE) distribution in Cable-in-Conduit Conductors ( CICCs ) used for fusion grade

magnets,” Fusion Eng. Des., vol. 88, no. 5, pp. 341–349, 2013.

[15] Dr. J. Krishnaraj and B. Prashanth. A Comprehensive Study on Various Welding

Techniques Used for Cryogenic Vessels. International Journal of Civil Engineering and

Technology, 8(6), 2017, pp. 171–177.

effect of mass flow rate on thermohydraulic ......lo2 at constant temperature of 70k . the result...

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