Presentation Title

Modeling and Analysis of a High Temperature, High Pressure, Two-Phase NH3/FAME-MLL PFHX

Faculty Mentor

Kevin Anderson

Start Date

17-11-2018 8:30 AM

End Date

17-11-2018 10:30 AM

Location

HARBESON 57

Session

POSTER 1

Type of Presentation

Poster

Subject Area

engineering_computer_science

Abstract

This presentation presents the analysis of a two-phase heat exchanger (HX) using Fatty Acid Methyl Ester Methyl Linoleate (FAME-MLL) and Ammonia (NH3) working fluids for use in Venus lander in-situ mission active thermal control applications. The physical characteristics of FAME resemble fossil diesel fuels mixed with vegetable oils. The FAME fluids are non-toxic, biodegradable, renewable, and alternative fuels. The FAME-MLL has a published triple point: 238.1 K, boiling point: 628.84 K, critical point: 700 K, 1.341 MPa, 238.05 kg/cubic meter and applicability range of 238.1 < T < 1000 K. The particular selection of the FAME-MLL working fluid is based on its critical temperature of 799 K which is larger than that of the local Venus environment of 738.15 K. Thus, using FAME-MLL takes advantage of latent heat transfer for a continuously operating heat rejection system. Obviously, designing a HX around the FAME-MLL working fluid is a challenge. The discretized enthalpy method is used to model the HX’s two-phase working fluid behavior. The HX model is developed in MATLAB using the NIST REFPROP database to model the behavior of the working fluids, Ammonia (NH3) and FAME-MLL in this instance. Due to the high temperature 738.15 K, high pressure 9 MPa, nature of this HX application, Plate-fin Heat Exchangers (PFHXs) are baselined for the design. The fins of the PFHX can arrange to operate in cross-flow, counter-flow and/or cross-counter-flow configurations. The PFHX has a high volume to area ratio, thus they are compact. Using Nickel based alloys for fabrication allows the PFHX to withstand extreme pressures (20 MPa for diffusion bonded PFHX), and extreme temperatures (on the order of 1100 K). The numerical model of the two-phase NH3/FAME-MLL PFHX is used to size the HX for the proper duty, thus specifying the configuration (crossflow, counter-flow, etc.) while determining the required heat transfer area, Log-Mean Temperature Difference, and Effectiveness-Number of Transfer Units parameter of the PFHX. The thermal-hydraulic pressure drop across the PFHX is modeled assuming a variety of passage cross-sections (triangular, rectangular, etc.) using the data from Kays and London (1984) for skin friction drag as a function of Reynolds number. The overall heat transfer coefficient of the PFHX is based on internal flow heat transfer correlations of Kays and London (1984).

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Nov 17th, 8:30 AM Nov 17th, 10:30 AM

Modeling and Analysis of a High Temperature, High Pressure, Two-Phase NH3/FAME-MLL PFHX

HARBESON 57

This presentation presents the analysis of a two-phase heat exchanger (HX) using Fatty Acid Methyl Ester Methyl Linoleate (FAME-MLL) and Ammonia (NH3) working fluids for use in Venus lander in-situ mission active thermal control applications. The physical characteristics of FAME resemble fossil diesel fuels mixed with vegetable oils. The FAME fluids are non-toxic, biodegradable, renewable, and alternative fuels. The FAME-MLL has a published triple point: 238.1 K, boiling point: 628.84 K, critical point: 700 K, 1.341 MPa, 238.05 kg/cubic meter and applicability range of 238.1 < T < 1000 K. The particular selection of the FAME-MLL working fluid is based on its critical temperature of 799 K which is larger than that of the local Venus environment of 738.15 K. Thus, using FAME-MLL takes advantage of latent heat transfer for a continuously operating heat rejection system. Obviously, designing a HX around the FAME-MLL working fluid is a challenge. The discretized enthalpy method is used to model the HX’s two-phase working fluid behavior. The HX model is developed in MATLAB using the NIST REFPROP database to model the behavior of the working fluids, Ammonia (NH3) and FAME-MLL in this instance. Due to the high temperature 738.15 K, high pressure 9 MPa, nature of this HX application, Plate-fin Heat Exchangers (PFHXs) are baselined for the design. The fins of the PFHX can arrange to operate in cross-flow, counter-flow and/or cross-counter-flow configurations. The PFHX has a high volume to area ratio, thus they are compact. Using Nickel based alloys for fabrication allows the PFHX to withstand extreme pressures (20 MPa for diffusion bonded PFHX), and extreme temperatures (on the order of 1100 K). The numerical model of the two-phase NH3/FAME-MLL PFHX is used to size the HX for the proper duty, thus specifying the configuration (crossflow, counter-flow, etc.) while determining the required heat transfer area, Log-Mean Temperature Difference, and Effectiveness-Number of Transfer Units parameter of the PFHX. The thermal-hydraulic pressure drop across the PFHX is modeled assuming a variety of passage cross-sections (triangular, rectangular, etc.) using the data from Kays and London (1984) for skin friction drag as a function of Reynolds number. The overall heat transfer coefficient of the PFHX is based on internal flow heat transfer correlations of Kays and London (1984).