Building Hydronic Systems — Pressure Profile — For HVAC Project Managers

This post is in 2 parts.

Part-1 we deal with the theory.  The basic Hydrostatic equation and the Bernoulli’s equation.

I have used the customary US engineering units throughout.  This is mostly because almost all texts these days have a detailed SI units treatment of these equations and very little or none in IP units.

This is a big disadvantage for young engineers joining the HVAC field.  Hopefully this will help.

 

Building Hydronic Pressure Profile Part-1

Building Hydronic Pressure Profile Part-2

 

 

 

Pump Cavitation – A look Under The Hood

The original talk on this topic was a Power Point presentation.  The PDF attached does not have the benefit of the verbal commentary along with the slides.But it still conveys some key concepts and should prove useful.  (There is some “inside” humor sprinkled around, as the original was intended for my own Company Project Engineers – please ignore.)

 

Pump Cavitation NPSH

The Curious Definition of “Fan Static Pressure” Part-1

Many HVAC engineers work their entire careers and retire without realizing that what they always thought of as Fan Static Pressure is not how ASHRAE, AMCA or the fan manufacturer’s define Fan Static Pressure (FSP). The concept of Fan Static Pressure is a purely “defined” one – there is no direct measurement in the field that corresponds to “Fan Static Pressure”. FSP is commonly confused by Engineers with the Fan Static Pressure Rise or Duct Static Pressure Rise.

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Duct System Losses Are Total Pressure Losses

Confusion in the use of the terms STATIC PRESSURE and TOTAL PRESSURE is widely prevalent among HVAC Engineers and Contractors. There are serious consequences of not distinguishing clearly between the two, and one example would be that you make troubleshooting more difficult and in some cases impossible.

This article clarifies the distinction between Static Pressure and Total Pressure.

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A Closer Look At Condensing Boiler Efficiency PART-I

Mat Ansari PE

The art of peddling Boilers has shifted from the realms of Logic and Thermodynamics to sheer magic and out-of-context truths.  It is becoming imperative for Engineers like myself, who get involved with selecting Boilers maybe four or five times a year, to educate ourselves about the basic facts of boiler efficiency.  In this series of posts we will take a closer look at the work-horse of our industry – the common commercial gas fired hot water boiler in the 2 million BTU input range.  The posts will attempt to investigate the realistic level of efficiencies that might be expected from these boilers. We will assume that no special “heat recovery” contraptions are in use.

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A Closer Look At Condensing Boiler Efficiency PART-II

Mat Ansari PE

As we discussed in the previous post, when discussing boiler efficiency we must be very specific about the operating parameters of the boiler.

So in part-II here, we are going to be more specific and look at a 2MM BTUH input hot water boiler working under the following conditions:

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A Closer Look At Condensing Boiler Efficiency PART-III

Mat Ansari PE

Dew Point Temperature Of Flue Gas

One of the key concepts that needs to be clearly understood when discussing boiler efficiency is the concept of the Dew Point Temperature of the Flue Gases.  (Or more specifically the Dew Point of the water vapor in the flue gas.)  If you are going to design a HW Boiler installation, you must be aware of what the Flue Gas Dew Point is going to be.  In fact, flue gas dew point becomes even more important if your boiler is of the Non-Condensing type.  Ignoring this critical piece of design information can be very costly.

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A Closer Look At Condensing Boiler Efficiency PART-IV

Mat Ansari PE

Sensible Heat Loss in Dry Flue Gases

Now let us examine the second category of energy loss – the loss of sensible heat of hot flue gasses being vented to outside.  In Equation 6 above we have 18.5 lbs. of dry hot flue gas (products of combustion) being vented out of the stack.  The specific heat of dry products of combustion is approximately 0.24 BTU/lb. °F.

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Understanding The Stack Effect

All young Engineers and Architects who are going to be involved with the design of tall buildings need to thoroughly understand the concept of Stack Effect. By thorough I mean not just ASHRAE formulas but solid concepts on what this phenomenon is doing to the building and how it can work against your design intent and the proper operation of the building.

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