ISO 15758-2014 pdf free download.Hygrothermal performance of building equipment and industrial installations Calculation of water vapour diffusion Cold pipe insulation systems
Performance hygrothermique des équipements de bâtiments et installations industrielles — Calcul de Ia diffusion de vapeur d’eau — System es d ‘isolation de tuyau teries froides.
5 Boundary conditions
The following boundary conditions for temperature and vapour pressure shall be used to evaluate the formulae given in Clause 4.
a) At surface of cold pipe
The surface temperature of the cold pipe shall be taken as the temperature of the medium in the pipe. The vapour pressure at the surface shall be taken as the saturated vapour pressure at that temperature, i.e. a relative humidity of 1,0.
b) Ambient air
Outside buildings, use the monthly mean temperature and vapour pressure of the warmest month.
Inside buildings, use the temperature and vapour pressure representative of the use of the building in the warmest month of the year. Methods for deriving internal conditions are given in ISO 13788.
NOTE Use of the monthly mean vapour pressure gives results which are on the safe side.
6 Calculation procedure
6.1 General
The formulae given in Clause 4 allow the calculation of the total amount of water condensing within the cold pipe insulation and determination of whether condensation occurs within the insulation material or only on the pipe surface.
For the evaluation of the amount of water vapour transported into an insulated cold pipe system the following procedures shall he followed step by step.
6.2 Calculation of rate of condensation in single homogenous insulation layer
a) Define the service temperature of the cooling medium and the temperature and relative humidity of the environment.
b) Determine the vapour pressure corresponding to the given climatic conditions.
c) Calculate the amount of water uptake using Formula (8).
6.3 Calculation of rate of condensation in multi-layer insulation system
a) Define the service temperature of the cooling medium and the temperature and relative humidity of the environment.
b) Calculate the temperature distribution through the insulation in accordance with ISO 12241.
c) Calculate the saturation pressure distribution as a function o temperature in accordance with