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Technical Center

Delphi Corporation's Mexico Technical Center is a 620,000 square foot complex that was designed to centralize research operations for 5,000 engineers and technicians.  It is truly a world-class building.  In 2002, Mexican President Vicente Fox bestowed his country's prestigious National Technology Award to the Mexico Technical Center.  In its first four years of operation, technical center employees earned more than 30 U.S. patents, and have began the process to gain more than 100 others. Mexico Technical Center customers include major vehicle manufacturers around the world, as well as support for the 57 Delphi operations in Mexico.

Bath's scope of work on this remarkable building included the design of mechanical and electrical systems.  The project included six air-cooled chillers connected in parallel delivering 1,500 tons of chilled water to a variable flow hydronic system and three boilers delivering 17,000 kBtu/hr to the hot water system.  Both hydronic systems were piped in a primary/secondary/tertiary arrangement.

The HVAC design criteria for comfort called for indoor temperature to be 74 degree F plus or minus 2 degree F when outdoor ambient temperature was 105 degree F in the summer and 20 degree in the winter.  The indoor humidity level was to be in the 35% to 50% range. In general, the building was to be maintained at a positive pressure of +0.05 inches water column with respect to the outdoors with a range of plus or minus 0.02 inches. The laboratory area was to be maintained at less positive pressure with respect to adjacent areas of the building.

Infiltration of uncontrolled flow of air was a major concern to the owner.  The amount of infiltrated air was calculated using the crack method described in the ASHRAE handbook of fundamentals. To maintain the building at a positive pressure with respect to the outside, the pressure difference was determined by the sum of the pressure difference caused by stack effect and the pressure difference caused by wind.  The pressure difference caused by wind was calculated with an average wind velocity of 15mph and pressure difference caused by stack effect was calculated with an average neutral pressure level height of 50 ft.  The minimum pressurizing pressure difference was calculated to be 0.06 inches water column.

In the laboratory area, some of the process equipment required direct extraction of air for proper operation. The extraction of air density in the new laboratory area was calculated to be 0.55 cfm/ft2.

A major concern was that the process equipment dissipated great amounts of heat.  In order to avoid the over- or under-sizing the ventilation system in the laboratory area, Bath¡¦s design engineers worked with Delphi¡¦s process engineers to determine the amount of heat dissipation of such equipment.

In this project, a Direct Digital Control (DDC) system was specified to optimize the operations of the HVAC system to maintain comfort conditions at minimum energy use.  The control strategies included the control of pressure and flow in the water systems to transport the thermal energy generated in the chiller/boiler central plant to the terminal units. Another control strategy of the DDC system was sequencing the multiple chiller/boiler installation in response to the cooling/heating demand.

A subsequent modification to the building provided mechanical and electrical systems to technology testing laboratories.  The environmental conditions for these laboratories required 70F degree plus or minus 1 degree F and no more than 20% relative humidity.  A desiccant dehumidification system was designed to achieve the very dry environmental condition of 20% relative humidity.  Before designing the desiccant dehumidification system, the possibility of using mechanical refrigeration to achieve the environmental conditions was explored.  The moisture removal required an air dew point temperature of 39„aF.  This low air dew point temperature created a problem with the condensate freezing on the cooling coil.  Therefore, mechanical refrigeration for this application was rejected.

The desiccant dehumidification system consisted of the rotary absorbent wheel rotating through two chambers designated as the process and regeneration.  To properly size all components of the dehumidification system, a psychometric analysis was necessary to establish the thermodynamic properties of air entering and leaving through all components of the dehumidification system.  The table below illustrates the results of the psychometric analysis of the dehumidification system.