Lecture Objectives:

• Finish with thermal storage systems

• Plumbing • Hydronic distribution systems

–Chiller/Boiler – Storage – Building

Installation of Thermal Storage System

DownstreamUpstream

• Increases chiller efficiency • Increases chiller capacity • Overall system efficiency ??? • Decreases storage capacity• Simplifies system layout• …..

• Decreases chiller efficiency• Decreases chiller capacityOverall system efficiency ???• Increases storage capacity•……• Does not allow chiller shut down!

Modeling

Write energy and mass balancer equation for each section

Plumbing Arrangement for Chillers

(and Boilers)• Primarily water circulation loop only

• Primarily & Secondary circulation loops

• Primarily & Secondary & Tertiary loops

• ….

Reading assignment:

Chilled Water Plant Design Guide (Section 4)http://energydesignresources.com/media/2305/EDR_DesignGuidelines_CoolToolsChilledWater.pdf

Hydronic systems for district cooling/heating and buildings

Constant-Flow System, Single Chiller, Single Coil Constant-Flow System, Single Chiller, Multiple Coils

Mixing valve that control by-pass flow Major pumping force is the chiller pump

Control of coil temperature Mixing valve that control the flow through the coil Flow Variation as a Function of Valve Position

Major pumping force is the chiller pump

Same pressure drop like a cooling coil

Multiple chiller (or boilers) Parallel Serial

Primary-Loop Only VariableSpeed Flow

Single chiller Multiple chillers

Primary and Secondary Loop Variable Flow Design

Parallel chillers

Serial chillers

Large Plant or Building Distribution Systems

Primary/Secondary Loops with Variable Flow and Distributed Pumping

Primary/Secondary and Tertiary Pumping

Primary Pump ArrangementsDedicate a pump for each chiller

Provide a common header for the pumps

Coil Pumping Strategies

Variable speed pumps vs. Single pas Valve vs. Mixing valves vs. Diverting Valves

Impact of Piping Coil

Plumbing Arrangement in Building’s hydronic systems

Fan coil systems Baseboard heaters

Radiators

Hydronic Terms

• Head loss

• Open-loop vs. closed loop

Head Loss

Fittings

g

Vkh

2

2

Pumps• Raise pressure and produce flow

• Main type• Centrifugal

Inline Base mounted

Example of Turbine pump

Pump curves

• NPSHR = Net Positive Suction Head Required

Changing Pump Speed

Curve for Multiple Pumps

Net Positive Suction Head(cavitation)