A numerical approach to energy savings in heat drying process of drilled and water-cleaned PCB
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Abstract
The post-drill cleaning process, one of processes to manufacture Printed Circuit Boards (PCBs), can be divided into water cleaning and heat drying processes. The various contaminants occurred during the drilling process are removed in the water cleaning process. The remaining moisture after this process is thoroughly removed by vaporization during the heat drying process. In this paper, the heat drying process of PCBs that have been drilled and water-cleaned prior to drying, is modeled and investigated for a Computational Fluid Dynamics (CFD) analysis. The Human-Machine Interface (HMI) system configured by using the Ubiquitous Sensor Node (USN) and the Machine-to-Machine (M2M) device is proposed in order to measure interior temperatures of the drying system and to define boundary conditions for the CFD analysis. Currently, six heaters are in operation by workers for the heat drying process as customary. However, it was shown through the experimental measurement and numerical analysis that the heat drying process is possible with operating only 4 heaters. The electrical power consumption of the case where 4 heaters are operated shows 33% of decrease from that of the case where 6 heaters are operated. For a near future study, a structural improvement of the drying system will be proposed with research on parameters that are influential on the performance of the system as one of the measures for a further reduction of electrical power consumption.
Keywords
Post-drill cleaning Heat drying process CFD analysis M2M device HMI system Electrical power consumptionNomenclature
- A
area of dryer wall
- Cp
specific heat of fluid
- esta
internal energy of a fluid
- h
convective heat transfer coefficient
- hsta
static enthalpy
- htot
total enthalpy
- m
mass flow of hot air flown in through air knives
- mout
mass flow of hot air going out the exhaust
- N
points where temperature is measured or interpolated
- p
pressure of fluid
- Qin
heat flown in through air knives
- Qlate
latent heat
- Qout
heat going out the exhaust
- Qwall
heat going out through the outer wall
- T
temperature of fluid
- SM
momentum source term
- SE
energy source term
- U
velocity of fluid
- λ
thermal conductivity
- ρ
density of fluid
- τ
shear stress by fluid
- [K]
coefficient matrix
- [R]
vector of the right hand side of discretized equations
- [X]
solution vector
- ∇
gradient operator
- ⋇
tensor product of two vectors
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