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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
Sources 
Planar and volume sources provide regions of defined source 
of heat or momentum, or fixed values of velocities, 
concentration, and/or temperature. The following options are 
available: 
• Prescribed source of heat, concentration, and/or 
momentum 
• Fixed values of velocity, concentration, and/or 
temperature 
• Linear source of heat, concentration, and/or 
momentum given by the expression: 
source = coefficient (value - velocity or temperature) 
The last option also allows the specification of a pressure drop 
that varies linearly with (velocity), rather than (velocity) 2 , 
which is defined through planar resistances. A pressure drop 
term is seen as a source term in the conservation of 
momentum equation (equation 5.3). A linear source of 
momentum can be arranged to replicate this term, as follows: 
• Source = coefficient(value - velocity) 
Considering the x-coordinate direction and setting value 
= 0, we obtain: 
• Source* = -coefficient x x velocity x 
Which can be seen to be equivalent to: 
• DP = -f x x velocity x 
Supplies 
Supplies are to bring air in from outside, normally, 
conditioned air from the main plant. The flow is set using: 
• Fixed mass flow rate (kg/s) 
• Linear pressure drop/flow rate fan characteristic 
The temperature and angle of flow of incoming air can be 
specified. 
Thin Walls 
Internal thin walls are thin solid surfaces within the solution 
domain that are aligned with the grid. Solution is carried out 
on both sides. The walls are impervious to flow but it is 
possible to specify heat transfer across them. Surface friction 
(different on each side if required) is evaluated. 
Triangular Prisms 
Triangular prisms are solid objects with a triangular cross 
section, and with all faces except the sloping face aligned 
with x, y, and z. All surfaces are zero friction and only the 
sloping surface has heat transfer. This is specified in terms of 
a temperature and heat transfer coefficient, or, as a fixed heat 
flux. 
