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Heating System Design: Choosing a Heating System, Fuel Type, and Heat Transfer Medium - Pr, Assignments of Architecture

The University of Texas at AustinArchitecture
Prof. Jeffrey A. Siegel

An overview of the process of designing a heating system, including choosing a heating system, fuel type, and heat transfer medium. Topics covered include the objectives of heating system design, selecting a heating system and fuel type based on efficiency, cost, availability, and safety considerations, and choosing a heat transfer medium between steam and water. The document also includes examples of pipe sizing calculations and discussions on steam tables and water properties. Additionally, it touches upon the use of air as a heating medium and the importance of auxiliary systems and water treatment.

Typology: Assignments

Pre 2010

Uploaded on 08/26/2009

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Objectives
• Choose a heating system
• Describe required auxiliary equipment
• Calculate pipe sizes for water and steam
systems
• Reading 5.1-5.4, 5.6, parts of 5.7 & 5.8
Choosing a Heating System
• What is it going to burn?
• What is it going to heat?
• How much is it going to heat it?
• What type of equipment?
• Where are you going to put it?
• What else do you need to make it work?
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Download Heating System Design: Choosing a Heating System, Fuel Type, and Heat Transfer Medium - Pr and more Assignments Architecture in PDF only on Docsity!

Objectives

  • Choose a heating system
  • Describe required auxiliary equipment
  • Calculate pipe sizes for water and steam

systems

  • Reading 5.1-5.4, 5.6, parts of 5.7 & 5.

Choosing a Heating System

  • What is it going to burn?
  • What is it going to heat?
  • How much is it going to heat it?
  • What type of equipment?
  • Where are you going to put it?
  • What else do you need to make it work?

Choosing a Fuel Type

  • Availability
    • Emergencies, back-up power, peak demand
  • Storage
    • Space requirements, aesthetic impacts, safety
  • Cost
    • Capital, operating, maintenance
  • Code restrictions
    • Safety, emissions

Gas vs. Electricity

  • Which is more efficient?
  • Which is cheaper?
  • Which is easier?
  • Which is safer?

Choosing Water Temperature

  • Low temperature water (180 °F – 240 °F)
    • single buildings, simple
  • Medium (250-350 °F) and high temperature

(over 350 °F)

  • Groups of buildings where steam isn’t viable/ needed
  • Requires high temperature and pressure equipment
    • Nitrogen system to prevent steam formation

Choosing Steam Pressure

  • Low pressure (<15 psig)
    • No pumping for steam
    • Requires pumping/gravity for condensate
  • Medium and high-pressure systems
    • Often used for steam loads or larger loads

Steam Tables

  • ASHRAE HVAC Systems and Equipment (2000) , Chapter 10
  • ASHRAE Fundamentals (2001) , Chapter 6, Table 3
  • Basis of Table 5-2 in your text

Pipe Sizing Example

  • 1 inch pipe (ID)
  • Medium-temperature water (250°F) at 2.5 fps
    • Return water at 120 °F
    • q = M×C×ΔT
    • q=ρ×Q×C×ΔT
    • q = 375 kBTU/hr
      • Text (Table 5-2) is a little lower. Why?
      • Also, note “MBH” = 100 BTU/hr

What About Air?

  • Really bad heat transfer medium
    • Very low density and specific heat
    • Requires electricity for fans to move air
    • Excessive space requirements for ducts
  • But
    • Can be combined with cooling
    • Lowest maintenance
    • Very simple equipment

Equipment

  • Load demand, load profile
    • Amount and type of heat
    • Response time
  • Efficiency
    • 80 – 85% is typical
    • Electricity is ~100%
    • Heat pump is 120 - 250%
  • Combustion air supply
    • Flue gas discharge (stack height)

Choosing a Boiler

  • Fuel source
  • Transfer medium
  • Operating temperatures/pressures
  • Equipment
    • Type
      • Water tube
      • Fire tube
      • Electric resistance/electrode
    • Space requirements
    • Auxiliary systems

Boilers

  • Water Tube Boiler
    • Water in tubes, hot combustion gasses in shell
      • Quickly respond to changes in loads
  • Fire Tube Boiler
    • Hot combustion gasses in tubes, water in shell
      • Slower to respond to changes in loads

Auxiliary

  • Burner type (atmospheric or power vented)
  • Feedwater systems
    • Returns steam condensate (including accumulator)
    • Adds water to account for blowdown and leaks
    • Preheats the water
    • Removes dissolved gasses
  • Blowdown system
    • Periodically drain and cool water

Auxiliary

  • Water treatment
    • Dissolved minerals and gasses cause:
      • Reduced heat transfer
      • Reduced flow (increased pressure drop)
      • Corrosion
  • Treatment options
    • Chemical (add bases, add ions, add inhibitor)
    • Temperature (heat to remove oxygen)

Furnaces

  • Simpler than boilers
  • Electric = toaster
  • Natural gas or oil
    • Venting (atmospheric, induced draft, power venting)
    • Heat exchanger
    • Controls (limit switches, igniters, etc.)

Summary

  • Describe all major components of a heating

system

  • Calculate water and steam pipe diameters/sizes
  • Next week: Cooling Systems - Reading Assignment: 4.1 - 4.