Unmet Hours - RSS feedhttps://unmethours.com/questions/Question-and-Answer Resource for the Building Energy Modeling CommunityenWed, 22 Jul 2020 17:39:02 -0500Furnace Efficiency DOE-2/EnergyPLushttps://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/In the EnergyPlus documentation, for the description of the part-load fraction performance curve for the furnaces, it says: "This [...] performance curve [...] parameterizes the variation of gas consumption rate by the heating coil as a function of the part load ratio [...]. For any simulation timestep, the nominal gas consumption rate (heating load/burner efficiency) is divided by the part-load fraction (PLF) if a part-load curve has been defined."
DOE-2 calculates the HIR-op as the product of the rated HIR and the HIR-FPLR(PLR).
I compared the default (when using a template) EnergyPlus performance curve for the PLF and the default curve for HIR-FPLR(PLR) in eQUEST. They are pretty pretty similar! Which makes me thinks that we can consider that PLF = HIR-FPLR(PLR).
The HIR for a particular time step is ratio the of fuel used to the heating energy produced.
According to the DOE-2 definition we have:
Conso-op = f(Conso-rated * HIR-FPLR(PLR))
According to the EnergyPlus definition we have:
Conso-op = f(Conso-rated / PLF)
Which is not the same thing and makes me think that PLF <> HIR-FPLR(PLR) ... Am I missing something?Thu, 21 May 2015 18:45:22 -0500https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/Answer by Jeremy for <p>In the EnergyPlus documentation, for the description of the part-load fraction performance curve for the furnaces, it says: "This [...] performance curve [...] parameterizes the variation of gas consumption rate by the heating coil as a function of the part load ratio [...]. For any simulation timestep, the nominal gas consumption rate (heating load/burner efficiency) is divided by the part-load fraction (PLF) if a part-load curve has been defined."</p>
<p>DOE-2 calculates the HIR-op as the product of the rated HIR and the HIR-FPLR(PLR).</p>
<p>I compared the default (when using a template) EnergyPlus performance curve for the PLF and the default curve for HIR-FPLR(PLR) in eQUEST. They are pretty pretty similar! Which makes me thinks that we can consider that PLF = HIR-FPLR(PLR).</p>
<p>The HIR for a particular time step is ratio the of fuel used to the heating energy produced.</p>
<p>According to the DOE-2 definition we have:
Conso-op = f(Conso-rated * HIR-FPLR(PLR))</p>
<p>According to the EnergyPlus definition we have:
Conso-op = f(Conso-rated / PLF)</p>
<p>Which is not the same thing and makes me think that PLF <> HIR-FPLR(PLR) ... Am I missing something?</p>
https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?answer=8174#post-id-8174 A little update as it might be useful for other users.
Neal's answer made sense the way he presented it. However, it didn't quite add up with the data I had. To find out what the calculation is in both cases, I generated hourly reports in both eQUEST and EnergyPlus. Here is what I found out:
Calculation of the fuel consumption in DOE-2:
----------------------------------------
- Calculation of the PLR: PLR = (Load
for the hour) / (Total Furnace
Capacity)
- Use the PLR to get the HIR f(PLR)
using the performance curve attached
to the system
- Calculation of the operational HIR:
HIR-op = HIR f(PLR) * HIR-rated
- Fuel consumption: Qfuel = (Total
Furnace Capacity) * HIR-op **(eq. 1)**
Here is an excerpt from an hourly report from eQUEST that illustrate the calculation:
![](/upfiles/14328309961947271.png)
In this example, the total furnace capacity is 39988 Btu/h and the rated HIR is 1.25.
Calculation of the fuel consumption in EnergyPlus:
----------------------------------------
- Calculation of the PLR: PLR = (Load for the hour) / (Total Furnace Capacity)
- Use the PLR to get the PLF f(PLR) using the performance curve attached to the system
- Fuel consumption: Qfuel = (Total Furnace Capacity) * PLR * HIR-rated / PLF **(eq. 2)**
Here is an excerpt from an hourly report from EnergyPlus that illustrate the calculation:
![](/upfiles/14328310998487336.png)
In this example, the total furnace capacity is 39988 Btu/h and the rated HIR is 1.25.
Comparison:
----------------------------------------
Then, if we look at **(eq. 1)** and **(eq. 2)**:
- HIR f(PLR) * HIR-rated = PLR *
HIR-rated / PLF
- Which simplifies to HIR f(PLR) = PLR
/ PLF
- Thus **PLF = PLR / HIR f(PLR)**
In conclusion PLF and HIR f(PLR) are not quite the same.
Using this relation I converted the curve used in eQUEST (by default) to the match the PLF used in EnergyPlus.
- EnergyPlus PLF = f(PLR) is the default curve used in EnergyPlus
- eQUEST PLF = f(PLR) is the default curve used in eQUEST converted to the EnergyPlus "format".
![](/upfiles/14328312079749204.png)Thu, 28 May 2015 11:59:53 -0500https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?answer=8174#post-id-8174Comment by Jono for <p>A little update as it might be useful for other users.</p>
<p>Neal's answer made sense the way he presented it. However, it didn't quite add up with the data I had. To find out what the calculation is in both cases, I generated hourly reports in both eQUEST and EnergyPlus. Here is what I found out:</p>
<h2>Calculation of the fuel consumption in DOE-2:</h2>
<ul>
<li>Calculation of the PLR: PLR = (Load
for the hour) / (Total Furnace
Capacity)</li>
<li>Use the PLR to get the HIR f(PLR)
using the performance curve attached
to the system</li>
<li>Calculation of the operational HIR:
HIR-op = HIR f(PLR) * HIR-rated</li>
<li>Fuel consumption: Qfuel = (Total
Furnace Capacity) * HIR-op <strong>(eq. 1)</strong></li>
</ul>
<p>Here is an excerpt from an hourly report from eQUEST that illustrate the calculation:</p>
<p><img alt="" src="/upfiles/14328309961947271.png"/></p>
<p>In this example, the total furnace capacity is 39988 Btu/h and the rated HIR is 1.25.</p>
<h2>Calculation of the fuel consumption in EnergyPlus:</h2>
<ul>
<li>Calculation of the PLR: PLR = (Load for the hour) / (Total Furnace Capacity)</li>
<li>Use the PLR to get the PLF f(PLR) using the performance curve attached to the system</li>
<li>Fuel consumption: Qfuel = (Total Furnace Capacity) * PLR * HIR-rated / PLF <strong>(eq. 2)</strong></li>
</ul>
<p>Here is an excerpt from an hourly report from EnergyPlus that illustrate the calculation: </p>
<p><img alt="" src="/upfiles/14328310998487336.png"/></p>
<p>In this example, the total furnace capacity is 39988 Btu/h and the rated HIR is 1.25.</p>
<h2>Comparison:</h2>
<p>Then, if we look at <strong>(eq. 1)</strong> and <strong>(eq. 2)</strong>:</p>
<ul>
<li>HIR f(PLR) * HIR-rated = PLR *
HIR-rated / PLF</li>
<li>Which simplifies to HIR f(PLR) = PLR
/ PLF</li>
<li>Thus <strong>PLF = PLR / HIR f(PLR)</strong></li>
</ul>
<p>In conclusion PLF and HIR f(PLR) are not quite the same.</p>
<p>Using this relation I converted the curve used in eQUEST (by default) to the match the PLF used in EnergyPlus.</p>
<ul>
<li>EnergyPlus PLF = f(PLR) is the default curve used in EnergyPlus</li>
<li>eQUEST PLF = f(PLR) is the default curve used in eQUEST converted to the EnergyPlus "format".</li>
</ul>
<p><img alt="" src="/upfiles/14328312079749204.png"/></p>
https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?comment=46038#post-id-46038Amazing post! I remember scratching my head about this when I first started using e+ / os, I stopped using it for a while and recently started back up and encountered the exact same issue! This post refreshed my memory. Thanks so much!Wed, 22 Jul 2020 17:39:02 -0500https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?comment=46038#post-id-46038Comment by Neal Kruis for <p>A little update as it might be useful for other users.</p>
<p>Neal's answer made sense the way he presented it. However, it didn't quite add up with the data I had. To find out what the calculation is in both cases, I generated hourly reports in both eQUEST and EnergyPlus. Here is what I found out:</p>
<h2>Calculation of the fuel consumption in DOE-2:</h2>
<ul>
<li>Calculation of the PLR: PLR = (Load
for the hour) / (Total Furnace
Capacity)</li>
<li>Use the PLR to get the HIR f(PLR)
using the performance curve attached
to the system</li>
<li>Calculation of the operational HIR:
HIR-op = HIR f(PLR) * HIR-rated</li>
<li>Fuel consumption: Qfuel = (Total
Furnace Capacity) * HIR-op <strong>(eq. 1)</strong></li>
</ul>
<p>Here is an excerpt from an hourly report from eQUEST that illustrate the calculation:</p>
<p><img alt="" src="/upfiles/14328309961947271.png"/></p>
<p>In this example, the total furnace capacity is 39988 Btu/h and the rated HIR is 1.25.</p>
<h2>Calculation of the fuel consumption in EnergyPlus:</h2>
<ul>
<li>Calculation of the PLR: PLR = (Load for the hour) / (Total Furnace Capacity)</li>
<li>Use the PLR to get the PLF f(PLR) using the performance curve attached to the system</li>
<li>Fuel consumption: Qfuel = (Total Furnace Capacity) * PLR * HIR-rated / PLF <strong>(eq. 2)</strong></li>
</ul>
<p>Here is an excerpt from an hourly report from EnergyPlus that illustrate the calculation: </p>
<p><img alt="" src="/upfiles/14328310998487336.png"/></p>
<p>In this example, the total furnace capacity is 39988 Btu/h and the rated HIR is 1.25.</p>
<h2>Comparison:</h2>
<p>Then, if we look at <strong>(eq. 1)</strong> and <strong>(eq. 2)</strong>:</p>
<ul>
<li>HIR f(PLR) * HIR-rated = PLR *
HIR-rated / PLF</li>
<li>Which simplifies to HIR f(PLR) = PLR
/ PLF</li>
<li>Thus <strong>PLF = PLR / HIR f(PLR)</strong></li>
</ul>
<p>In conclusion PLF and HIR f(PLR) are not quite the same.</p>
<p>Using this relation I converted the curve used in eQUEST (by default) to the match the PLF used in EnergyPlus.</p>
<ul>
<li>EnergyPlus PLF = f(PLR) is the default curve used in EnergyPlus</li>
<li>eQUEST PLF = f(PLR) is the default curve used in eQUEST converted to the EnergyPlus "format".</li>
</ul>
<p><img alt="" src="/upfiles/14328312079749204.png"/></p>
https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?comment=8176#post-id-8176This makes sense to me. I couldn't remember if PLR was implicit in the HIR curve in DOE-2, or accounted for separately.Thu, 28 May 2015 13:00:26 -0500https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?comment=8176#post-id-8176Answer by Neal Kruis for <p>In the EnergyPlus documentation, for the description of the part-load fraction performance curve for the furnaces, it says: "This [...] performance curve [...] parameterizes the variation of gas consumption rate by the heating coil as a function of the part load ratio [...]. For any simulation timestep, the nominal gas consumption rate (heating load/burner efficiency) is divided by the part-load fraction (PLF) if a part-load curve has been defined."</p>
<p>DOE-2 calculates the HIR-op as the product of the rated HIR and the HIR-FPLR(PLR).</p>
<p>I compared the default (when using a template) EnergyPlus performance curve for the PLF and the default curve for HIR-FPLR(PLR) in eQUEST. They are pretty pretty similar! Which makes me thinks that we can consider that PLF = HIR-FPLR(PLR).</p>
<p>The HIR for a particular time step is ratio the of fuel used to the heating energy produced.</p>
<p>According to the DOE-2 definition we have:
Conso-op = f(Conso-rated * HIR-FPLR(PLR))</p>
<p>According to the EnergyPlus definition we have:
Conso-op = f(Conso-rated / PLF)</p>
<p>Which is not the same thing and makes me think that PLF <> HIR-FPLR(PLR) ... Am I missing something?</p>
https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?answer=8081#post-id-8081 The HIR in DOE-2 is the inverse of the heating efficiency (eff).
In DOE-2 the calculated efficiency is: 1/(HIR*HIR-FPLR(PLR))
In EnergyPlus the calculated efficiency is: eff/PLF
So if eff = 1/HIR, then PLF and HIR-FPLR(PLR) are the same.Fri, 22 May 2015 10:23:06 -0500https://unmethours.com/question/8072/furnace-efficiency-doe-2energyplus/?answer=8081#post-id-8081