• Heat transfer rate mainly depends upon convection (major source of heat removal) and some by radiation. Q = h x A x ΔT is the formula where ‘h’ is the Convective coefficient and depends upon the mass flow rate of fluid, (i.e. air in the telecom shelter). ‘A’ is the area exposed for air to come in contact with the PCM profiles. ‘ΔT’ is the temperature difference which is of the user’s interest.
• Heat transfer rate mainly depends upon convection (major source of heat removal) and some by radiation.  Q = h x A x ΔT is the formula where ‘h’ is the Convective coefficient and depends upon the mass flow rate of fluid, (i.e. air in the telecom shelter). ‘A’ is the area exposed for air to come in contact with the PCM profiles. ‘ΔT’ is the temperature difference which is of the user’s interest.
• Since placement of profiles in a shelter is constrained by the placement of the BTS (Base Transreceiver Station) unit, batteries, power interface units or switching equipment, the profiles containing PCM are placed only in the free area available. Hence, not all the surface area is available for heat transfer.
• Generally, for good fluid flow in a shelter, 2-3 fans with the specifications of approx. 50W, 24V/48V DC, and 3000 RPM are recommended. Lower RPM fans will reduce the air circulation and may hamper necessary heat transfer.
• Locations of the fans depend entirely on the position of the PCM profiles and other Electronic equipment.
• Theoretically, for one hour back-up, for 1kWh, 20 kg of savE™ HS 29 is required, based on the latent heat of savE™HS 29. This translates to 240 kgs of HS 29 for four hour backup with 3kWh heat source.
• For four hour back-up 3kW x 4 hrs (12kWh) an exposed (in direct contact with air) area with a minimum of 27 m2 of surface is required. The number of savE™ HS 29 profiles of 4 kgs (0.4 Sqm)  mm is usually 70 profiles for this exposed area (translating it to 280 kgs of HS 29). While using the 2.8kgs profiles (0.3 Sqm), the requirement of both area and salt quantity is met by using only 86 profiles (translating it to 240kgs only).
• It may be noted that it is not only the quantity of salt essential for desired backup but also a minimum of exposed surface for heat absorption. This may at times necessiate additional profiles.
• In general, the position & number of profiles and fans will vary from shelter to shelter. It is strongly advised that individual testing and experimentation be done by the Shelter manufacturer/installer to determine the optimum:
  • number of profiles required
  • placement of profiles
  • location of fans
  • RPM of fans for effective heat distribution/direction towards profiles

• The PCM panels  are mounted on-site  approximately  30° from vertical. Three to four such racks can be put on one frame, having the facility of mounting 35-60 PCM panels. The upper three sections in each rack are normally left empty for effective air circulation provided by a DC fan (24V/48V)  placed on top of the frame. Two different pattern of racks are available.

PCM Benefits for Shelters

The diagram above shows the effects of using PCM inside a telecom enclosure. It defines the duration when the air-conditioning is “switched off.” The rise in temperature is rapid without PCM. However, with PCM installed, the rise in temperature is delayed as much of the equipment heat energy gets absorbed. Thus, the temperature inside the enclosure remains constant (rT) for a longer duration than without the assistance of any conventional cooling system.  Using active or passive can later discharge the heat energy absorbed cooling systems during off-peak hours, making the PCM available for another cycle.

The R-value of foam is higher per inch than other types of insulation

• The R-value of insulation materials is dependent on ambient temperature and wind conditions. Independent tests show that at 18 degrees F, with a 15 mph wind, the theoretical R-value of urethane foam drops from 19 to 18, while batt insulation drops from 19 to 7.
• In retrofits with smaller existing framing sizes, this means that buildings can still be insulated to meet current code requirements.
• In new construction this means that smaller framing sizes (lower lumber costs and larger rooms) can still be insulated to today’s energy efficient standards.
• Plumbing can be installed in outside walls without freezing because only a thin layer of foam is required between pipes and the outside sheathing.
• This is effective in bays with steel columns, which have a very small space available for insulation between the steel and the sheathing.

Foam is a good air sealant

• Air leakage is the number one cause of poor building performance. Foam insulated homes out-perform conventionally insulated homes without requiring complicated and labor-intensive air sealing details.
• Because foam is air tight, it performs better in windy conditions and resists R-value loss.
• Batt insulation has virtually no air sealing ability and has to rely on other components of a total thermal envelope to maintain performance levels.
• Air leakage at penetrations creates an environment for condensation. This affects overall performance and can compromise indoor air quality (bugs, mold, and rot). Condensation can also lead to premature structural failure in structural framing and sheathing materials.
• Independent testing shows that urethane insulated buildings can perform as much as ten times better than today’s energy standards.

Foam bonds to the structure

• Foam will not compress or settle.
• Foam adheres to steel decking on flat roof structures providing effective insulation where venting is impossible and there is no framing cavity to support other types of insulation.

Foam can have structural advantages

• Foam can help to resist wind shear.
• Foam can serve to reinforce exterior sheathing and windows.
• Urethane foams are used in structural panels and other composite structures.
• Foam can be walked on or nailed into without damaging its performance. It can also be washed without damage.

Foam systems perform well for some types of sound control

• Both open and closed-cell foams provide good sealing against air-borne sound transmission.
• Both open and closed-cell foams provide good STC ratings against air-borne sound transmission.
• No low-density insulation materials are effective against structure-borne sound. Double layer structural systems, resilient structural materials, or massive structures are the best defense against structure-borne sound.