Thermal insulation work using insulation materials is performed on equipment and piping having high temperature contents, in order to reduce thermal energy losses, to stabilize operations, and to take safety measures. Strictly speaking, the insulation is never completely adiabatic, and since the rate of heat loss and the surface temperature of the thermal insulation material will differ depending on its thickness, it is necessary to find the optimum insulation thickness after clarifying the prerequisites when determining the actual insulation construction specifications. In this document, the contents specified in JIS-A9501 (“Hoon Horei Kouji Sekou Hyoujun” in Japanese: “Heat and Cold Insulation Construction and Installation Standard”) are introduced as an example of the method for calculating the thickness of the thermal insulation material. (Y. Kawai)
For the design of multi-tubular heat exchangers, environments are being developed through commercial software enhancements to easily achieve designs that can minimize costs with satisfactory heat transfer performances. On the other hand, it is important to estimate the size of a heat exchanger in advance before executing rigorous calculations. Here, we will examine the influence of dominant factors (film heat transfer coefficients, and fouling resistance) on the overall heat transfer coefficient. (H. Taguchi)
The approximate equation widely used as the heat transfer equation for heat exchangers is "Q = U * A * ΔT". The logarithmic mean temperature (LMTD) is commonly used as the temperature difference (ΔT) in the heat transfer equation, but there are cases in which it is directly applied to systems with phase changes without consideration on how the LMTD is derived. In this study, we will examine the implications of applying the LMTD to systems in which phase changes occur. (H. Taguchi)
In petrochemical plants, CS (carbon steel) is generally used as an equipment material, unless there are issues related to corrosion or other process requirements. In an actual production plant, it is sometimes necessary to change the material of CS equipment due to originally unexpected causes (such as erosion, or external surface corrosion, etc.). When this happens, the size of the equipment must often remain similar due to the location where it is installed. Particularly, when the equipment is a heat exchanger, a detailed examination is necessary because changing the material will affect the equipment capacity. It is important, to know beforehand the degree of sensitivity of a material upgrade on the heat transfer capacity. (Y. Kawai)
