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A B C D E F G H I J K L M N O P
Packaged units, specification of, Packing characteristic, in cooling towers, Packings, for cooling towers Packings, for fixed beds: Packinox heat exchanger, Paints, spectral characteristics of reflectance of surfaces treated with, Palen, J W Panchal, C B, Paraffins, normal and isonormal: Paraldehyde: Parallel channel instability, in condensers, Partial boiling in subcooled forced convective heat transfer, Participating media, radiation interaction in, Particle convective component, in heat transfer from fluidized beds, Particle emissivity, Particle Reynolds number in fixed beds, Particles: Particulate fluidization, Particulate fouling, Pass arrangements, in plate heat exchangers, Passes, tube side, Passive methods, for augmentation of heat transfer, passive systems for: PD5500 mechanical design of shell-and-tube heat exchangers to, Peacock, D K, Pearson number, Peclet number Peng-Robinson equation of state, application to hydrocarbons, Penner's rule, in absorption of radiation by gases, Pentachloroethane (Refrigerant 120): Pentadecane: Pentadecene: Pentadiene 1, 2: Pentadiene 1, trans 3: Pentadiene 1, 4: Pentadiene 2-3: Pentafluoroethane (Refrigerant 125) Pentamethylbenzene: Pentane: Pentanoic acid: 1-Pentanol: 1-Pentene: cis-2-Pentene: trans-2-Pentene: Pentylacetate: Pentylbenzene: Pentylcyclohexane: Pentylcyclopentane: Pentylcyclopropane, liquid properties, Perforated fins, in plate fin heat exchangers, Perforated plates, loss coefficients in, Periodic operation, of regenerator, Periodic variations in temperature, thermal conduction in bodies with, PFR correlation, for heat transfer in high fin tube banks, Pharmaceutical industry, fouling of heat exchangers in, Phase change materials, in augmentation of heat transfer, Phase change number, Phase equilibrium: Phase inversion Phase separation, as source of corrosion problems, Phenol: Phenols: Phenylhydrazine: Phonons, in thermal conductivity of solids, Phosgene: Physical properties: Pi theorum, in dimensional analysis, Pinch analysis, for heat exchanger network design, Pioro, I L Pioro, LS, Pipe leads, Piperidine: Pipes, circular: Pipes, noncircular: Piping components: Pitting corrosion, in stainless steels, Planck's constant, Planck's law, for spectral distribution of blackbody radiation, Plane shells, steady-state thermal conduction in, Plastic deformation Plate fin heat exchangers Plate fins, efficiency, Plate heat exchangers: Plate evaporator Plates: Plug flow: Plug flow model, for furnaces, Pneumatic conveyance, Pneumatic conveying dryer, P-NTU method: Polarization, of thermal radiation, Polyglycols, as heat transfer media, Polymers: Pool boiling, Porous surfaces: Port arrangements, in plate heat exchangers, Portable fouling unit, Poskas, P, Postdryout heat transfer: Powders: Power law fluid (non-Newtonian), Power plant: Prandtl number Precipitation (crystallization) fouling, Precipitation hardening, of stainless steels, Pressure coefficient: Pressure control of condensers, Pressure drop: Pressure gradient: Pressure, specification of in mechanical design to EN13445, Pressure testing, Pressure vessels, principle codes for, Pressurised water reactor, fouling in, Printed circuit heat exchanger, Problem table algorithm, in pinch analysis, Process heaters: Progressive plastic deformation Prolate spheroids, free convective heat transfer from, Promoters, in dropwise condensation, Propadiene: Propane: 1-Propanol: 2-Propanol: Propeller agitator, Property ratio method, for temperature dependent physical property Propionaldehyde: Propionic acid: Propionic anhydride: Proprionitrile: Propyl acetate: Propylamine: Propylbenzene: Propylcyclohexane: Propylcyclopentane: Propylene: 1,3-Propylene glycol: Propylene oxide: Propyl formate: Propyl propionate: Pseudo-boiling in supercritical fluids, Pseudo-film boiling in supercritical fluids, Pseudocritical pressure, Pseudocritical tempertaure, Pugh, S F Pulp and paper industry, fouling of heat exchangers in, Pulsations, use in augmentation of heat transfer, Pulverized fuel water-tube boiler, Pumping, lost work in, Pushkina and Sorokin correlation, for flooding in vertical tubes, Pyramid, free convective heat transfer from, Pyridine:
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Calculation Procedure for a Rating Problem

DOI 10.1615/hedhme.a.000304



3.9.9 Calculation procedure for a rating problem

This section outlines a step-by-step procedure for the thermal calculations involved in a rating problem. Steps 4–9 are required for each fluid stream.

  1. Surface geometry parameters: Given β, Af /A, and Dh, calculate γ and σ for each stream.

  2. Using the given heat exchanger size, calculate the frontal mass velocity (Gfr) for each stream, then calculate Gc (= Gfr /σ).

  3. Estimate the heat exchanger thermal effectiveness (ε) to allow calculation of the average fluid temperature for each stream. This may be based on an outright guess, or a preliminary calculation following steps 4–12.

  4. Evaluate fluid properties (pm, ηm, cpm) at the estimated average fluid temperature.

  5. Calculate Re = DhGc /ηm.

  6. Determine f and j (or Nusselt number Nu) from f and j versus Re plots for the surface, or from tabled laminar flow solutions, where appropriate.

  7. Calculate the heat transfer coefficient, α = jGccpmPr2/3 or α = Nuk /Dh.

  8. Calculate fin efficiency. With ml = (2α /kδ)1/2l calculated, the fin efficiency (ηf) is determined from the appropriate fin efficiency chart or equation.

  9. Calculate surface efficiency, η0 = 1 – (1 – ηf ) Af /A.

  10. Calculate heat transfer surface areas and determine UA. A simpler approach is to use the given heat exchanger volume (V) and calculate UA from

    \[ \frac{1}{UA}=\left(\frac{1}{\eta_{s}\alpha A}\right)_{\!1}+R_{w}+\left(\frac{1}{\eta_{s}\alpha A}\right)_{\!2}=\frac{1}{V}\left[\left(\frac{1}{\eta_{s}\alpha\lambda}\right)_{\!1}+\frac{a}{2k_{w}}(b_{1}+b_{2}+2_{a})+\left(\frac{1}{\eta_{s}\alpha\lambda}\right)_{\!2}\right] \]

    where subscripts 1 and 2 refer to stream 1 and 2, respectively, and V = heat exchanger volume, γ1 = A1 /V, ηs = fin surface efficiency, λ = tube thermal conductivity, A1 = Surface area on side 1, and A2 denotes surface are on side 2, and Rw = tube wall thermal resistance

  11. Calculate Cmin /Cmax and NTU = UA /Cmin.

  12. Using the parameters in step 11, determine ε from the ε-NTU-Cmin /Cmax chart (or equation) for the given heat exchanger flow arrangement. The ε-NTU chart or equation can be found in most heat transfer textbooks.

  13. Compare the calculated ε with estimated ε. Repeat steps 4–12 as necessary to obtain desired convergence of ε.

Nomenclature

Acexchanger minimum free flow area
Afexchanger total fin area on one side
Afrexchanger total frontal area
bplate spacing (or rectangular fin height)
Cflow stream capacity rate (cp);  Cc (cold fluid),  Ch (hot fluid),  Cmin (minimum),  Cmax (maximum)
cpspecific heat at constant pressure
Dhhydraulic diameter of any internal passage (Dh = 4rh = 4AcL /A)
fmean friction factor, defined on the basis of mean surface shear stress
Gcflow stream mass velocity based on minimum flow area, cp /Ac
Gfrflow stream mass velocity based on flow frontal area, cp /Afr
Ltotal heat exchanger flow length; also, flow length of uninterrupted fin
mfin effectiveness parameter (2α /kδ)1/2
mass flow rate
NTUnumber of heat transfer units of an exchanger (= UA /Cmin)
NuNusselt number (αDh /k)
Rflow stream capacity rate ratio (= Cmin /Cmax)
rhhydraulic radius (AcL /A)
Uunit overall thermal conductance
Vvolume
αconvection heat transfer coefficient
βratio of total heat transfer area on one side of a plate-fin heat exchanger to the volume between the plates on that side
γratio of total transfer area on one side of the exchanger to total volume for the exchanger
δfin thickness
εheat exchanger thermal effectiveness, dimensionless
ηdynamic viscosity
ηffin efficiency, dimensionless
ηsfin surface efficiency, dimensionless
λthermal conductivity
σratio of free-flow area to frontal area, Ac /Afr, dimensionless
Subscripts
mmean conditions, defined as used
maxmaximum
minminimum

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