HVAC 2 - Study Guide

Water

The ideal energy transportation medium with a high specific heat and density, inexpensive, nontoxic, and readily available.

Ethylene Glycol

Substance added to water to lower its freezing point.

Water Loop

Circulation paths in water systems including from chiller to cooling tower, chiller evaporator to AHU cooling coils, etc.

Significant Pressure Losses

Pressure losses incurred as water moves through pipes in a hydronic system.

Fluid Flow Basics

Energy balance concepts and formulas for adiabatic, steady flow of a fluid in a conduit.

Bernoulli’s Principle

Describes the total pressure as the sum of static pressure and velocity pressure for incompressible fluid.

Reynolds Number

Dimensionless number used to determine flow characteristics: <2300 is laminar, 2300-4000 is transient, >4000 is turbulent.

Friction Loss

Losses in energy from traveling through the piping system due to friction.

Dynamic Viscosity

A measure of a fluid's resistance to flow, affecting friction and flow behavior.

Pump Purpose

To overcome pressure losses and circulate water through a piping system.

Best Efficiency Point (BEP)

The flow rate at which a pump operates at optimum efficiency.

Cavitation

The formation of vapor bubbles in a fluid due to low pressure, potentially damaging pumps.

Open Loop System

A system where pressure is equal to atmospheric pressure, often involving elements like cooling towers.

Closed Loop System

A system designed to maintain pressure above atmospheric, requires components like expansion tanks.

Duct System Components

Elements comprising a duct system, including straight ducts and fittings.

Fan Surge

A phenomenon that occurs when a fan approaches blocked tight static pressure points, leading to noise and vibration.

Centrifugal Fans

Fans that can handle higher pressures, often used in air handling units.

Axial Fans

Compact fans that move large volumes of air with lower static pressure.

Capacity Control Dampers

Devices that change system characteristics by adding resistance and modulating airflow.

Theoretical Single-stage Vapor-compression Cycle

Cycle involving one compressor, highlighting isentropic processes and constant pressure operations.

Actual Single-Stage Refrigeration Cycle

Cycle that includes superheating refrigerant at the compressor inlet and sub-cooling at condenser outlet.