cooling systems 2 Flashcards
What are the four loops in a typical air-handling system?
Refrigerant loop, heat-rejection loop, chilled-water loop, air-side loop.
Where is the chiller system usually located in a building?
Typically in the basement for protection and centralized access.
What does the heat-rejection loop do in a chiller system?
Transfers heat from the chiller to a cooling tower where it is dissipated into the air.
How is chilled water distributed in a chiller system?
Pumped from the chiller to individual air-handling units on each floor.
What is a fan coil system?
A system with individual fan coil units providing localized heating/cooling without ductwork.
What is a major advantage of fan coil units?
Localized control and reduced need for ductwork, lowering ceiling height requirements.
How is outside air typically introduced in fan coil systems?
Directly through the exterior wall near each fan coil unit.
What is a DX system?
A Direct Expansion system where the refrigerant is directly used for cooling without chilled water.
How is the DX system beneficial to developers?
Allows flexibility for tenants to install their own systems with minimal developer investment.
What is a DX RTU?
A packaged rooftop unit with built-in refrigerant cycle, fan, and coil, often used in retail or tenant spaces.
What are the pros of a DX RTU system?
Simple, off-the-shelf, low-cost, and easy to install.
What are the cons of a DX RTU system?
Shorter lifespan due to exposure and inefficiency in long-term ownership.
What factors affect duct sizing?
Heat loss per zone, CFM requirements, and static pressure.
Why are rectangular ducts often used?
They fit better in shallow ceiling spaces and are cheaper to install.
What is the benefit of round ducts?
Less air friction and better shape retention, especially when exposed.
What is static pressure in duct systems?
Resistance caused by air friction and bends, affecting fan sizing and energy use.
What tool is used to balance CFM and static pressure for duct sizing?
A ductulator.
What does a reheat do?
Adds heat to conditioned air before it enters spaces that need warming.
What is the difference between CAV and VAV systems?
CAV uses constant airflow with variable temperature; VAV uses variable airflow with constant temperature.
What are booster fans used for?
To maintain airflow pressure in long duct runs or areas with weak airflow.
What is a multi-pipe system?
A system using separate hot and cold water pipes to provide heating and cooling simultaneously.
