tailieunhanh - 1999 HVAC Applications Part 9

Tham khảo tài liệu '1999 hvac applications part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1999 ASHRAE Applications Handbook SI TO FROM LOAD A. CHARGING STORAGE TO FROM LOAD B. DISCHARGING STORAGE Fig. 15 Thermal Storage with Chiller Upstream the on-peak period the building load may be met by the chiller the storage or a combination of both Figure 15B . A downstream modulating valve maintains the chilled water supply to the building loop at the desired temperature. If demand limiting is desired the chiller electrical demand must also be controlled. The remainder of the load is met by the storage. Storage Tank Insulation Because of the low temperature associated with ice storage insulation is a high priority. In retrofit applications the current insulation must be evaluated to ensure there is no condensation or excessive heat loss. All ice storage tanks located above ground should be insulated to limit standby losses. For external melt ice-on-coil systems and some internal melt ice-on-coil systems the insulation and vapor barrier are part of the factory-supplied containers most other storage tanks require that insulation and a vapor barrier by applied in the field. Below-ground tanks used with ice harvesters may not need insulation below the first metre. Because the tank temperature does not drop below 0 C at any time there is no danger of freezing and thawing groundwater. All below-ground tanks using fluids below 0 C during the charge cycle should have a well designed and properly installed insulation and vapor barrier generally on the exterior. Interior insulation is susceptible to damage from the ice and should be avoided. Because a hydrated salt solution operates at chilled water temperatures of about 8 C the same insulation practices apply. ELECTRICALLY CHARGED HEAT STORAGE DEVICES Thermal energy can also be stored in electrically-charged thermally-discharged storage devices. For devices that use a solid mass as the storage medium equipment size is typically specified by the nominal power rating to the nearest kilowatt of the internal heating .