9/2003 Heat transfer review Heat transfer review What is required to size a heat exchanger What is required to size a heat exchanger Compact heat transfer solutions Compact heat transfer solutions –Plate Heat Exchanger –Spiral Heat Exchanger –Welded Plate Heat Exchangers –Specialty Plate Heat Exchangers Installation Photos Installation Photos Design of Heat Exchanger Solutions Design of Heat Exchanger Solutions Order Flow Process Order Flow Process Agenda

9/2003 Heat Transfer Basics

9/2003 Radiation Radiation –Electromagnetic waves –When it reaches a body it has 3 options: Reflected Absorbed Transmitted Convection Convection –Energy is transferred by the motion and intermixing of small mass elements –Natural convection caused by density difference –Forced convection is man-made (ex., pump) Conduction Conduction –Molecular or atomic vibrations –No material transport Three ways to transfer heat

9/2003 Laminar Laminar –Conduction: low heat transfer rate Turbulent Turbulent –Convection: high heat transfer rate –Film layer at the wall- Conduction - Low heat transfer Flow Principles

9/2003 Flows and temperatures for both sides Fluid properties including: density, specific heat, thermal conductivity, and viscosity for at least two points. For condensers and evaporators data such as a condensing curve, boiling point elevation, and/or other parameters may be required. Process conditions and limitations such as system pressure, potential for fouling or plugging, pressure drop limitations etc. The supplier may be able to use their experience to assist in determining proper values from above. Data needed to design a heat exchanger

9/2003

9/2003 Where Where Q = heat transferred (Kbtu/hr) m = mass flow rate (hot fluid) (lb/hr) C = specific heat (hot fluid) (Btu/lb,F) T = hot fluid entering temperature (F) T = hot fluid leaving temperature (F) HIHIHIHI HOHOHOHO p HIHIHIHI HOHOHOHO Q = m C p (T - T ) Heat Transfer

9/2003T HIHIHIHI T HOHOHOHO T COCOCOCO T CICICICI Temperature Length of Channel HIHIHIHI HOHOHOHO COCOCOCO CICICICI Q = m C p (T - T ) = m C p (T - T ) Thermodynamics at work!!

9/2003 Where Where Q = heat transferred U = overall heat transfer coefficient A = heat transfer surface area LMTD = log mean temperature difference Q = U A (LMTD) Heat Transfer

9/2003 (T -T ) - (T - T ) HIHIHIHI COCOCOCO HOHOHOHO CICICICI (T -T ) HIHIHIHI COCOCOCO HOHOHOHO CICICICI ln LMTD = T HIHIHIHI T HOHOHOHO T COCOCOCO T CICICICI Temperature Length of Channel Log Mean Temperature Difference

9/2003 = U A (LMTD) Q = mC p (T – T ) = U A (LMTD) HIHIHIHI HOHOHOHO Determining Heat Transfer Area m C (T - T ) U (LMTD) HIHIHIHI HOHOHOHO P A = Therefore Determining Proper “U” value is the key!!

9/2003 Items That Effect “U” value and Fouling Tendency Channel Geometry (turbulence) Fluid velocity and wall shear Fluid Properties (particularly viscosity) *Viscosity also has a major impact on the pressure drop that will be seen in the heat exchanger Tube Spiral Plate

9/2003 Hot FluidFouling LayersCold Fluid Metal Wall Film Boundary Layers Temperature Temperature Temperature Q = U A (LMTD) Heat Flow 1U1h + Rf 1htk ++= and

9/2003 Nusselt Number Prandtl Number Reynolds Number h Heat Transfer Basics – Three Wise Men

9/2003T HIHIHIHI T HOHOHOHO T COCOCOCOT CICICICI Temperature Length of Channel Lower LMTD and no temperature cross means less efficiency Cocurrent Flow