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ABSTRACT
Shell and tube heat exchangers are widely used for various industrial refrigeration applications. This paper summarizes previous studies performed on single tube and bundles and the correlations thereof developed for ammonia. There are limited studies available on ammonia boiling outside single tube and bundle. The major driving force behind this paper is that an extensive work is currently underway on the subject of direct expansion of ammonia on the outside of a tube bundle by the authors. As of now, there are no such studies available in the open literature. In order to understand the process, it is important to follow up on previous studies on pool and convective boiling on single tubes and bundles with ammonia.
Nomenclature
| Bo | = | Boiling number, |
| Cp | = | Specific heat capacity, J/kg K |
| D | = | Tube internal diameter, m |
| do | = | Bubble departure diameter, m |
| Fr | = | Froude number, (G2/ρ2gD) |
| F(pred) | = | Function depending on reduced pressure |
| G | = | Mean mass flux, kg/m2 s |
| g | = | Acceleration due to gravity, m/s2 |
| h | = | Heat transfer coefficient, W/m2 K |
| i | = | Enthalpy, J/kg |
| k | = | Thermal conductivity, W/m K |
| M | = | Molecular mass, kg/kmol |
| m | = | Mass, kg |
| N | = | Total number of tube rows in bundle. |
| n | = | Specific number of row in the bundle |
| Nu | = | Nusselt number, (hD/k) |
| n(pred) | = | Exponent of heat flux defined by Eq. (Equation5b |
| p | = | Pressure, N/m2 |
| Pr | = | Prandtl number, (μ Cp/k) |
| = | Heat flux, W/m2 | |
| = | Reference value of heat flux | |
| R | = | Characteristic length, m |
| Re | = | Reynolds number, (GD/μ) |
| Ra | = | Surface Roughness (ISO 4287/10), µm |
| Rao | = | Reference value of surface roughness, µm |
| Rp | = | Surface Roughness (DIN 4762 T.1/08.60), µm |
| T | = | Temperature, K |
| w | = | Mass concentration of lubricant, |
| x | = | Vapor quality |
| Y | = | Parameter for heat transfer correlation, (hsp/hg) |
| Greek Symbols | ||
| α | = | Thermal diffusivity, m2/s |
| β | = | Contact angle, degree |
| Γl | = | Average mass flow rate of sprayed liquid reaching a tube per unit tube length |
| ϵ | = | Parameter defined in Eq. (11a), (17a), (18a), (19a) |
| µ | = | Dynamic viscosity, kg/m s2 |
| ν | = | Kinematic viscosity, m2/s |
| ρ | = | Density, kg/m3 |
| σ | = | Surface Tension, N/m |
| Φ | = | Non dimensional heat flux |
| ψ | = | Multiplier for two phase heat transfer |
| ω | = | Parameter defined by Eq. (17b) |
| Subscripts | ||
| atm | = | Atmospheric conditions |
| crit | = | Critical |
| g | = | Saturated vapor |
| l | = | Saturated liquid |
| lg | = | Phase change |
| n | = | nth row |
| o | = | Reference value |
| red | = | Reduced |
| sat | = | Saturation |
| sp | = | Single phase |
| spn | = | Single, plain tube, no oil |
| spo | = | Single, plain tube, with oil |
| tp | = | Two phase |
Additional information
Notes on contributors
Ahmad Abbas
Ahmad Abbas received his B.S. (2010) in mechanical engineering from University of Engineering and Technology, Peshawar, Pakistan and M.S. (2012) in mechanical engineering from GIK Institute of Engineering Sciences and Technology. He is a Ph.D. scholar at the Natural Fluids Refrigeration Center, GIK Institute working on the project “Shell side direct expansion evaporation of ammonia on plain tube bundle with inlet quality and exit superheat effects”.
Zahid H. Ayub
Zahid H. Ayub is Technical Director at Isotherm, Inc., a manufacturer of heat transfer equipment. He holds Ph.D. (1986) in mechanical engineering from Iowa State University. He is recognized as one of the pioneers in the field of ammonia enhanced heat transfer. He has published more than hundred international journal and conference papers. He holds 11 United States patents. He is the recipient of Michigan New Product Award, ASHRAE Distinguished Service Award, ASHRAE Exceptional Service Award and 2017 Louise and Bill Holladay Distinguished Fellow Award. He is a fellow of ASME and ASHRAE. Represents United States on the Scientific Council of International Center for Heat and Mass Transfer and the IEA Heat Pump group. He is a registered professional engineer in the states of Michigan and Texas. An active member of ASME, ASHRAE, IIAR, AIChE, IoR (UK), IIR, Eurammon and Sigma Xi Honor Research Society. Served as chair of the ASHRAE standing committee on refrigeration and a member of ASHRAE Research Advisory Panel for Strategic Policy development 2010–2015. Has been active member of ASHRAE TC1.3 and TC8.5 and the ASME K-10 Committee since 1987. He is the founder and director of Natural Fluids Refrigeration Center (NFRC), GIK Institute. Serves as Adjunct Professor at the University of Texas-Arlington and GIK Institute. He has served as the technology editor for the International Journal of Enhanced Heat Transfer, associate editor of ASME Journal of Thermal Science and Engineering Applications and is currently executive editor of the Journal of Heat Transfer Engineering.
Tariq S. Khan
Tariq S. Khan received his B.S. (1997) and M.S. (1999) in mechanical engineering from Eastern Mediterranean University, Turkish Republic of North Cyprus, and a Ph.D. (2010) in mechanical engineering from GIK Institute of Engineering Sciences and Technology, Pakistan. His doctoral dissertation was on evaporation in flooded corrugated plate heat exchanger with ammonia and ammonia/miscible oil, an ASHRAE-sponsored project. He is currently working as a Research Associate at the Petroleum Institute, Abu Dhabi. His diversified research work in thermo-fluids has been published in international journals and presented at various international conferences.
Adnan H. Ayub
Adnan H. Ayub is President of Isotherm, Inc., in Arlington, Texas. He holds B.S. (2005) in mechanical engineering from Rose-Hulman Institute of Technology, M. Eng (2008) and D.Eng. (2016) in mechanical engineering from Texas A&M University. His doctoral work was on the design of a unique shell side direct expansion evaporator. His area of expertise is design of heat exchangers according to ASME, PED, and DNV classifications. He holds a U.S. and international patent on a novel evaporator. He has authored several journal and conference papers. He is an active member of ASME, ASHRAE, IIAR, and GPSA.
Javed A. Chattha
Javed A. Chattha holds Ph.D. (1990) in mechanical engineering from University of Birmingham, UK. Currently he is serving as a Professor in the Faculty of Mechanical Engineering and Pro-Rector (Academics) at GIK Institute of Engineering Sciences and Technology, Pakistan. His Ph.D. work was on heat transfer modeling of transparent honeycomb insulation and energy simulation of transparently insulated buildings. His current interests also include micro-hydro power generation and performance evaluation of IC engines with biodiesel.