Download
1 / 25
250 likes | 429 Views
slide 2. The EU CENSE project (Oct. 2007 - March 2010). Aim of the project:To accelerate adoption and improved effectiveness of the EPBD related CEN- standards in the EU Member States These standards were successively published in the years 2007-2008 and are being implemented or planned to be i
E N D
1. Calculation of the integrated energy performance of buildings EN 15316: Heating systems in buildings Method for calculation of system energy requirements and system efficiencies Part 4-1: Space heating generation systems, combustion systems (boilers) Laurent SOCAL
EDILCLIMA/ Italy socal@iol.it
2. slide 2 The EU CENSE project (Oct. 2007 - March 2010) Aim of the project:
To accelerate adoption and improved effectiveness of the EPBD related CEN- standards in the EU Member States
These standards were successively published in the years 2007-2008 and are being implemented or planned to be implemented in many EU Member States. However, the full implementation is not a trivial task
Main project activities:
To widely communicate role, status and content of these standards; to provide guidance on the implementation
To collect comments and good practice examples from Member States aiming to remove obstacles
To prepare recommendations to CEN for a “second generation” of standards on the integrated energy performance of buildings
3. slide 3 Brief introduction A brief introduction to the CENSE project and the CEN-EPBD standards is provided in a separate presentation:
4. slide 4 More information More information and downloads: www.iee-cense.eu
5. FITTING INTO THE CALCULATION SCHEME slide 5 This standard is part of a series (EN 15316) for the calculation of heating system energy requirements and system efficiencies.
The whole series of EN standards is a modular structure.
The information going from one block to the next is kWh and, within systems, heating medium temperatures and flow rates.
The balance shall be repeated for each calculation interval and the results summed to get yearly values.
More details on the general calculation scheme can be found in EN 15603 and EN 15316-1.This standard is part of a series (EN 15316) for the calculation of heating system energy requirements and system efficiencies.
The whole series of EN standards is a modular structure.
The information going from one block to the next is kWh and, within systems, heating medium temperatures and flow rates.
The balance shall be repeated for each calculation interval and the results summed to get yearly values.
More details on the general calculation scheme can be found in EN 15603 and EN 15316-1.
6. slide 6 This standard does not cover solid fuel boilers and air heaters which are treated as dedicated parts (EN 15316-4-6 and prEN 15316-4-7 respectively).
Specific parts of EN 15316-4 are dedicated to other generation devices (heat pumps, solar systems, etc.) as well (see figure 2).
Boiler sizing is not covered by this standard. This standard is intended to calculate the in-use energy performance of a given boiler, either existing or as designed and sized.
This standard does not cover solid fuel boilers and air heaters which are treated as dedicated parts (EN 15316-4-6 and prEN 15316-4-7 respectively).
Specific parts of EN 15316-4 are dedicated to other generation devices (heat pumps, solar systems, etc.) as well (see figure 2).
Boiler sizing is not covered by this standard. This standard is intended to calculate the in-use energy performance of a given boiler, either existing or as designed and sized.
7. More than 1 generator? slide 7 The complete calculation flow for a heating and domestic hot water system is as follows:
start with building needs calculation (2 zones heating and 1 zone d.h.w. as shown)
continue the calculation adding up losses of each subsystem until you reach storage and distribution
give priority to the appropriate generation subsystem (solar system in this case)
calculate priority generation subsystem first (solar system according to EN 15316-4-3 as shown) and get required input energy per each energy carrier
calculate the back-up generation subsystem then (boiler according to EN 15316-4-1 as shown) and get required input energy per each energy carrier
get total delivered energy as the sum of energy inputs to all generators, per energy carrier (see NOTE for auxiliary energy simplification in this example)
convert delivered energy into primary energy according to your national primary energy factor (… or to CO2 emission or whatever) per each energy carrier
get the total primary energy
get the system efficiency as the ratio of needs to corresponding primary energy
NOTE: to simplify the picture, auxiliary energy has been considered in the generation subsystems only. Any auxiliary energy used in the other subsystems (i.e. distribution, emission, etc.) shall be added to the electricity carrier total and some recovery might be considered in the relevant subsystems.The complete calculation flow for a heating and domestic hot water system is as follows:
start with building needs calculation (2 zones heating and 1 zone d.h.w. as shown)
continue the calculation adding up losses of each subsystem until you reach storage and distribution
give priority to the appropriate generation subsystem (solar system in this case)
calculate priority generation subsystem first (solar system according to EN 15316-4-3 as shown) and get required input energy per each energy carrier
calculate the back-up generation subsystem then (boiler according to EN 15316-4-1 as shown) and get required input energy per each energy carrier
get total delivered energy as the sum of energy inputs to all generators, per energy carrier (see NOTE for auxiliary energy simplification in this example)
convert delivered energy into primary energy according to your national primary energy factor (… or to CO2 emission or whatever) per each energy carrier
get the total primary energy
get the system efficiency as the ratio of needs to corresponding primary energy
NOTE: to simplify the picture, auxiliary energy has been considered in the generation subsystems only. Any auxiliary energy used in the other subsystems (i.e. distribution, emission, etc.) shall be added to the electricity carrier total and some recovery might be considered in the relevant subsystems.
8. Calculation principles Objective: to calculate fuel and auxiliary energy consumption to fulfill the heat demand of the attached distribution subsystem(s)
Basic input data: heat required by the attached distribution sub-system(s) QH,dis,in
The calculation method takes into account
heat losses (flue gas, envelope, etc.)
auxiliary energy use and recovery
other input data :
location of the heat generator(s) (heated room, unheated room, ..)
operating conditions (time schedule, water temperature, etc.)
control strategy (on/off, multistage, modulating, cascading, etc.)
Basic outputs is delivered energy as:
fuel consumption EH,gen,in
auxiliary energy consumption WH,gen,aux slide 8 The three methods calculate fuel and auxiliary energy consumption of one or more boilers to fulfill the heat demand of the attached distribution subsystem(s).
The methods take into account boiler heat losses and/or recovery due to the following physical factors:
flue gas losses (burner on);
draught losses (burner stand-by);
envelope losses (burner on and stand-by);
auxiliary energy use (standby/electronics, gas valve, pump, fan);
auxiliary energy recovery.
The three methods calculate fuel and auxiliary energy consumption of one or more boilers to fulfill the heat demand of the attached distribution subsystem(s).
The methods take into account boiler heat losses and/or recovery due to the following physical factors:
flue gas losses (burner on);
draught losses (burner stand-by);
envelope losses (burner on and stand-by);
auxiliary energy use (standby/electronics, gas valve, pump, fan);
auxiliary energy recovery.
9. Generation subsystem simplified energy balance slide 9 The basic inputs and outputs of the generation subsystem are shown.
The common input data is the heat required by the attached distribution sub-system(s) QH,dis,in. Optionally, the additional load for domestic hot water distribution subsystem QW,dis,in may be taken into account when using a single generator for both services.
Other input data is required to characterize:
type and characteristics of the heat generator(s) (atmospheric, condensing, etc.);
location of the heat generator(s) (heated room, unheated room, ..);
operating conditions (time schedule, water temperature, etc.);
control strategy (on/off, multistage, modulating, cascading, etc.).
The basic outputs are:
fuel consumption EH,gen,in;
auxiliary energy consumption WH,gen,aux;
that are used as an input in EN 15603 to calculate primary energy required by the heating system.
Other optional output information that may be extracted relates to:
generation total heat loss (flue gas, draught and envelope losses);
recoverable generation heat losses (explicit or already taken into account as a reduction of losses = recovered losses)
seasonal generation efficiency.
The basic inputs and outputs of the generation subsystem are shown.
The common input data is the heat required by the attached distribution sub-system(s) QH,dis,in. Optionally, the additional load for domestic hot water distribution subsystem QW,dis,in may be taken into account when using a single generator for both services.
Other input data is required to characterize:
type and characteristics of the heat generator(s) (atmospheric, condensing, etc.);
location of the heat generator(s) (heated room, unheated room, ..);
operating conditions (time schedule, water temperature, etc.);
control strategy (on/off, multistage, modulating, cascading, etc.).
The basic outputs are:
fuel consumption EH,gen,in;
auxiliary energy consumption WH,gen,aux;
that are used as an input in EN 15603 to calculate primary energy required by the heating system.
Other optional output information that may be extracted relates to:
generation total heat loss (flue gas, draught and envelope losses);
recoverable generation heat losses (explicit or already taken into account as a reduction of losses = recovered losses)
seasonal generation efficiency.
10. Available methods Case specific
Based on data declared according to Directive 2002/92/CE
Primarily intended for new or recent boilers for which this data is available
Boiler cycling
Primarily intended for existing systems and condensing boilers
Tabulated (precaculated) values
Simplification to cover common case and avoid calculation burden to estimate simple repetitive cases slide 10 3 methods have been defined because no single method provides a correct solution for all cases. A too simplified method may not be able to show the effect of improvements, whilst a detailed method may be unnecessarily time consuming for common situations.
The boiler typology method is based on data coming from direct measurements of the boiler efficiency (fuel in and heat out measured). It is a reliable and easily applied method, suitable for use by people with minimal modeling skills in common situations.
The boiler cycling method is based on a calculation of losses (indirect method). It has proven suitable for existing systems, where very few data are available. Simple formulas can be derived to calculate seasonal efficiency according to data collected during an inspection.
Precalculated values (according to the previous calculation methods). These values may be used for simple repetitive case (inspections?). If the assumptions for the precalculated values are not met (boundary conditions), boiler typology or boiler cycling method shall be used.
3 methods have been defined because no single method provides a correct solution for all cases. A too simplified method may not be able to show the effect of improvements, whilst a detailed method may be unnecessarily time consuming for common situations.
The boiler typology method is based on data coming from direct measurements of the boiler efficiency (fuel in and heat out measured). It is a reliable and easily applied method, suitable for use by people with minimal modeling skills in common situations.
The boiler cycling method is based on a calculation of losses (indirect method). It has proven suitable for existing systems, where very few data are available. Simple formulas can be derived to calculate seasonal efficiency according to data collected during an inspection.
Precalculated values (according to the previous calculation methods). These values may be used for simple repetitive case (inspections?). If the assumptions for the precalculated values are not met (boundary conditions), boiler typology or boiler cycling method shall be used.
11. Case specific method calculation procedure Get performance data in standard conditions at 3 reference power levels
Efficiencies at 100% and 30% load (according to Directive 92/42/EC)
Stand-by losses power [W] at 0% load
Correct data to take into account actual operating conditions (basically, the effect of water temperature in the boiler)
Calculate losses power at 30% and 100% from corrected efficiencies
Calculate losses at actual load by linear interpolation
Use the same interpolation approach (based on data at 0…30%...100% load) for auxiliary energy calculation slide 11 Parameters required to characterize the boiler for the case specific method are:
generator output at full load (reference boiler power);
generator efficiency at full load;
generator average water temperature at test conditions for full load;
generator efficiency at intermediate load;
generator average water temperature at test conditions for intermediate load;
stand-by heat losses at test temperature difference;
difference between mean boiler temperature and test room temperature in test conditions;
power consumption of auxiliary devices at full load;
power consumption of auxiliary devices at intermediate load;
stand-by power consumption of auxiliary devices;
minimum operating boiler temperature.
Full load and part load test data are generally available for new or recent boilers as they are required by the Boiler Efficiency Directive (92/42/EEC). For existing old boilers, these data are generally not available
Standby-losses and auxiliary power consumption data are generally not available.
Default data shall be given in a national annex to complete data for new boilers, and to use this method for existing boilers, as these factors are not easily measured directly.
Additional boiler input parameters are:
correction factor of full-load efficiency (depending on boiler type, condensing/non condensing);
correction factor of intermediate load efficiency.
No procedure to determine these data is given. They should be given in a national annex. Annex B of the standard gives default values for these factors.
Actual operating conditions input data are:
net heat output to the heat distribution sub-system(s);
average water temperature in the boiler;
return water temperature to the boiler (for condensing boilers);
boiler room temperature;
temperature reduction factor depending on the location of the generator.
Parameters required to characterize the boiler for the case specific method are:
generator output at full load (reference boiler power);
generator efficiency at full load;
generator average water temperature at test conditions for full load;
generator efficiency at intermediate load;
generator average water temperature at test conditions for intermediate load;
stand-by heat losses at test temperature difference;
difference between mean boiler temperature and test room temperature in test conditions;
power consumption of auxiliary devices at full load;
power consumption of auxiliary devices at intermediate load;
stand-by power consumption of auxiliary devices;
minimum operating boiler temperature.
Full load and part load test data are generally available for new or recent boilers as they are required by the Boiler Efficiency Directive (92/42/EEC). For existing old boilers, these data are generally not available
Standby-losses and auxiliary power consumption data are generally not available.
Default data shall be given in a national annex to complete data for new boilers, and to use this method for existing boilers, as these factors are not easily measured directly.
Additional boiler input parameters are:
correction factor of full-load efficiency (depending on boiler type, condensing/non condensing);
correction factor of intermediate load efficiency.
No procedure to determine these data is given. They should be given in a national annex. Annex B of the standard gives default values for these factors.
Actual operating conditions input data are:
net heat output to the heat distribution sub-system(s);
average water temperature in the boiler;
return water temperature to the boiler (for condensing boilers);
boiler room temperature;
temperature reduction factor depending on the location of the generator.
12. slide 12 The animation highlights the calculation procedure
Corrections of efficiencies are assumed to be linear according to average water temperature.
Condensation is not described well because it is strongly non-linear
The fixed intermediate point at 30% comes from the product standard. For the system standard the intemediate point should be modulation minimum.
A second order interpolation of the 3 points is also allowed in the standard.The animation highlights the calculation procedure
Corrections of efficiencies are assumed to be linear according to average water temperature.
Condensation is not described well because it is strongly non-linear
The fixed intermediate point at 30% comes from the product standard. For the system standard the intemediate point should be modulation minimum.
A second order interpolation of the 3 points is also allowed in the standard.
13. slide 13 Boiler directive data ??? Sometimes it is not easy to find boiler directive data… especially for old boilers like the 2 shown in the picture.Sometimes it is not easy to find boiler directive data… especially for old boilers like the 2 shown in the picture.
14. Boiler cycling generation energy balance slide 14 The diagram shows the detailed energy balance when using the boiler cycling method.
This method performs an analysis of boiler LOSSES.
Note that there are 2 contributions to auxiliary energy:
Auxiliary energy for the burner fan (Wbr) , which is dependent on the boiler load
Auxiliary energy for any primary pump (Wpmp) on the generation circuit, which is assumed to be constant power.The diagram shows the detailed energy balance when using the boiler cycling method.
This method performs an analysis of boiler LOSSES.
Note that there are 2 contributions to auxiliary energy:
Auxiliary energy for the burner fan (Wbr) , which is dependent on the boiler load
Auxiliary energy for any primary pump (Wpmp) on the generation circuit, which is assumed to be constant power.
15. Boiler cycling method For single stage burners, the calculation interval is divided into two basic operating conditions, with different specific losses:
Burner ON time, with flue gas and envelope losses
Burner OFF time , with draught and envelope losses
Loss factors are given as a percentage of combustion power (input to the boiler)
Loss factors are corrected according to operating conditions (water temperature in the boiler, load factor)
The required input load factor to meet output requirement is calculated
Modulating and multistage boilers are taken into account with a third reference state: burner ON at minimum power
Condensation heat recovery is taken into account as a reduction of flue gas losses with burner ON
slide 15 Basic boiler characterization input parameters for the boierl cycling method (single stage burner) are:
maximum combustion power of the generator (test conditions);
heat loss factors at test conditions for flue gas losses (burner on),
heat loss factors at test conditions for draught losses (burner stand-by)
heat loss factors at test conditions for envelope losses (burner on and stand-by);
average boiler water temperature at test conditions for burner on;
average boiler temperature at test conditions for burner off;
temperature of test room;
electrical power consumption of auxiliary appliances (before the generator, typically burner fan) and related recovery factor;
electrical power consumption of auxiliary appliances (after the generator, typically primary pump) and related recovery factor.
Full load and part load flue gas losses with burner on are generally available for new boilers and can easily be measured on existing boilers (see EN 15378, Annex C).
Standby-losses and power consumption data are not typically available, nor are they easily measured. Missing data shall be estimated using tables with default values. Annex C to 15316-4-1 gives an example of such tables
For condensing boilers, the following additional input data are required:
temperature difference between flue gas temperature and boiler return water temperature;
flue gas oxygen content.
For multi-stage and modulating burners, the following additional data are required:
minimum combustion power with burner on;
heat loss factors for flue gas losses (burner on) at minimum combustion power;
auxiliary energy power at minimum combustion power.
For multi-stage and modulating condensing boilers, the following additional data are required:
temperature difference between boiler return water temperature and flue gas temperature at minimum combustion power;
flue gas oxygen contents at minimum combustion power.
Additional boiler input parameters:
exponents n, m and p for the correction of heat loss factors.
No procedure to determine these data is given. They should be given in a national annex. Annex C to EN15316-4-1 gives an example of such tables.
Annex C to the standard contains a complete set of default parameters for this method that can be used as a reference and template to develop a national annex. The values shown are currently used in Italy.
Actual operating conditions input data:
net heat output to the heat distribution sub-system(s);
average water temperature in the boiler;
return water temperature to the boiler (for condensing boilers);
boiler room temperature;
reduction factor taking into account recovery of heat losses through the generator envelope, depending on location of the generator.
Basic boiler characterization input parameters for the boierl cycling method (single stage burner) are:
maximum combustion power of the generator (test conditions);
heat loss factors at test conditions for flue gas losses (burner on),
heat loss factors at test conditions for draught losses (burner stand-by)
heat loss factors at test conditions for envelope losses (burner on and stand-by);
average boiler water temperature at test conditions for burner on;
average boiler temperature at test conditions for burner off;
temperature of test room;
electrical power consumption of auxiliary appliances (before the generator, typically burner fan) and related recovery factor;
electrical power consumption of auxiliary appliances (after the generator, typically primary pump) and related recovery factor.
Full load and part load flue gas losses with burner on are generally available for new boilers and can easily be measured on existing boilers (see EN 15378, Annex C).
Standby-losses and power consumption data are not typically available, nor are they easily measured. Missing data shall be estimated using tables with default values. Annex C to 15316-4-1 gives an example of such tables
For condensing boilers, the following additional input data are required:
temperature difference between flue gas temperature and boiler return water temperature;
flue gas oxygen content.
For multi-stage and modulating burners, the following additional data are required:
minimum combustion power with burner on;
heat loss factors for flue gas losses (burner on) at minimum combustion power;
auxiliary energy power at minimum combustion power.
For multi-stage and modulating condensing boilers, the following additional data are required:
temperature difference between boiler return water temperature and flue gas temperature at minimum combustion power;
flue gas oxygen contents at minimum combustion power.
Additional boiler input parameters:
exponents n, m and p for the correction of heat loss factors.
No procedure to determine these data is given. They should be given in a national annex. Annex C to EN15316-4-1 gives an example of such tables.
Annex C to the standard contains a complete set of default parameters for this method that can be used as a reference and template to develop a national annex. The values shown are currently used in Italy.
Actual operating conditions input data:
net heat output to the heat distribution sub-system(s);
average water temperature in the boiler;
return water temperature to the boiler (for condensing boilers);
boiler room temperature;
reduction factor taking into account recovery of heat losses through the generator envelope, depending on location of the generator.
16. slide 16 Losses through the chimney with burner ON
Losses shall be corrected according to the operating water temperature.
Losses through the chimney with burner ON increase with flue gas temperature (approx. 1% every 20 °C). In turn, flue gas temperature increases just like the average water temperature in the boiler (return temperature for condensing boilers)
Losses through the envelope are controlled by the boiler insulation layer and are therefore proportional to the difference between average temperature in the boiler and boiler room temperature.
A small correction is also performed according to the load factor (exponential correction) to take into account the fact that at very low loads the losses are reduced.
Losses through the chimney with burner ON
Losses shall be corrected according to the operating water temperature.
Losses through the chimney with burner ON increase with flue gas temperature (approx. 1% every 20 °C). In turn, flue gas temperature increases just like the average water temperature in the boiler (return temperature for condensing boilers)
Losses through the envelope are controlled by the boiler insulation layer and are therefore proportional to the difference between average temperature in the boiler and boiler room temperature.
A small correction is also performed according to the load factor (exponential correction) to take into account the fact that at very low loads the losses are reduced.
17. slide 17 Losses through the chimney with burner OFF
Losses shall be corrected according to the water temperature.
Losses through the envelope are controlled by the boiler insulation layer and are therefore assumed to be proprotional to the difference between average temperature in the boiler and boiler room temperature.
Losses through the chimney with burner OFF increase with flue gas temperature and are assumed to be proportional to the difference between average temperature in the boiler and boiler room temperature.Losses through the chimney with burner OFF
Losses shall be corrected according to the water temperature.
Losses through the envelope are controlled by the boiler insulation layer and are therefore assumed to be proprotional to the difference between average temperature in the boiler and boiler room temperature.
Losses through the chimney with burner OFF increase with flue gas temperature and are assumed to be proportional to the difference between average temperature in the boiler and boiler room temperature.
18. slide 18 Boiler cycling diagram
This diagram shows graphically the calculation procedure for a single stage burner.
The vertical axis is power, as a percentage of combustion power.
The horizontal axis is time
Areas are therefore energies.
Areas with burner ON (minute 5 to 7 and 15 to 17)
Area E = A1+A2+B+C is the total energy of fuel burned during burner ON time (100% of combustion power multiplied by ON time)
Area A1 represents flue gas losses during burner ON time
?c is combustion efficiency. It can be measured according to EN 15378 annex C
Area A2 represents envelope losses during burner ON time
?u is net efficiency. It is the value declared by the manufacturer at 100% load , according to directive 94/42/CE
Area B + C is total heat delivered to the distribution subsystem during burner ON time
Area with burner OFF(minute 7 to 15)
Area B are losses through the envelope and through the chimney with burner OFF.
Area B is heat taken back from the distribution subsystem during burner OFF time. An equal area B shall therefore be canceled in the burner ON time graph, determining the seasonal efficiency. Area C is the actual net heat delivered to the distribution subsystem during an entire ON-OFF cycle.
Actual calculation procedure starts knowing area C and losses factors and determines the load factor.
When the load factor is known. Losses can be calculated.
Boiler cycling diagram
This diagram shows graphically the calculation procedure for a single stage burner.
The vertical axis is power, as a percentage of combustion power.
The horizontal axis is time
Areas are therefore energies.
Areas with burner ON (minute 5 to 7 and 15 to 17)
Area E = A1+A2+B+C is the total energy of fuel burned during burner ON time (100% of combustion power multiplied by ON time)
Area A1 represents flue gas losses during burner ON time
?c is combustion efficiency. It can be measured according to EN 15378 annex C
Area A2 represents envelope losses during burner ON time
?u is net efficiency. It is the value declared by the manufacturer at 100% load , according to directive 94/42/CE
Area B + C is total heat delivered to the distribution subsystem during burner ON time
Area with burner OFF(minute 7 to 15)
Area B are losses through the envelope and through the chimney with burner OFF.
Area B is heat taken back from the distribution subsystem during burner OFF time. An equal area B shall therefore be canceled in the burner ON time graph, determining the seasonal efficiency. Area C is the actual net heat delivered to the distribution subsystem during an entire ON-OFF cycle.
Actual calculation procedure starts knowing area C and losses factors and determines the load factor.
When the load factor is known. Losses can be calculated.
19. Modulating boilers slide 19 Multistage and modulating generators (effect of burner control) are taken into account by addition of a third reference state:
burner ON at minimum continuous power.
The performance of these boilers is calculated assuming that the following operating conditions are possible:
if the power required by the distribution system is less than the minimum ON power (left), the burner will operate cycling ON-OFF just as a single stage boiler but at minimum power;
if the power required by the distribution system is higher than the minimum ON power (right), the boiler will stay ON continuously and its loss factors are calculated by interpolation between minimum load and maximum load values.
Multistage and modulating generators (effect of burner control) are taken into account by addition of a third reference state:
burner ON at minimum continuous power.
The performance of these boilers is calculated assuming that the following operating conditions are possible:
if the power required by the distribution system is less than the minimum ON power (left), the burner will operate cycling ON-OFF just as a single stage boiler but at minimum power;
if the power required by the distribution system is higher than the minimum ON power (right), the boiler will stay ON continuously and its loss factors are calculated by interpolation between minimum load and maximum load values.
20. slide 20 For multi-stage and modulating burners, the following additional data are required:
minimum combustion power with burner on (manufacturer data or actual set value);
heat loss factors for flue gas losses (burner on) at minimum combustion power (can be measured);
auxiliary energy power at minimum combustion power.
This method takes into account two effects of modulating the burner power:
improved load factor (this reduces the impact of stand-by losses)
better efficiency at low loads (NOTE: for some types of burners, efficiency decreases at low load: this is taken into account as well)For multi-stage and modulating burners, the following additional data are required:
minimum combustion power with burner on (manufacturer data or actual set value);
heat loss factors for flue gas losses (burner on) at minimum combustion power (can be measured);
auxiliary energy power at minimum combustion power.
This method takes into account two effects of modulating the burner power:
improved load factor (this reduces the impact of stand-by losses)
better efficiency at low loads (NOTE: for some types of burners, efficiency decreases at low load: this is taken into account as well)
21. Condensing boiler slide 21 Condensation latent heat recovery is calculated according to flue gas composition and temperature. It is taken into account as a "bonus" (reduction) of flue gas losses with burner ON.
Flue gas temperature is calculated as the sum of:
water return temperature, which depends on the operating conditions of emitters and distribution system (heating system effect);
temperature difference between flue gas temperature and water return temperature (boiler effect).
The calculation is based on phisics and gives a good prediction of condensation latent heat recovery, taking corectly into account non linear effects.
Condensation latent heat recovery is calculated according to flue gas composition and temperature. It is taken into account as a "bonus" (reduction) of flue gas losses with burner ON.
Flue gas temperature is calculated as the sum of:
water return temperature, which depends on the operating conditions of emitters and distribution system (heating system effect);
temperature difference between flue gas temperature and water return temperature (boiler effect).
The calculation is based on phisics and gives a good prediction of condensation latent heat recovery, taking corectly into account non linear effects.
22. Flue gas temperature slide 22 Flue gas temperature diminishes until boiler outlet
Water termperature increases moving into the boiler
The final DT is a function of:
Heat exchager extension (boiler)
Actual istantaneous load Flue gas temperature diminishes until boiler outlet
Water termperature increases moving into the boiler
The final DT is a function of:
Heat exchager extension (boiler)
Actual istantaneous load
23. Why 3 methods No single method is the correct solution for all cases. A too simple method may not be able to show the effect of improvements whilst A detailed method may be time wasting for common repetitive situations.
The boiler typology method aims to extreme simplicity.
The case specific method is meant to use as far as possible boiler directive data.
The boiler cycling method is meant to deal with existing boilers/buildings, to keep a connection with directly measurable parameters (flue gas analysis) and to calculate operating performances of condensing boilers. slide 23
24. Parametering the methods Required data and default data for common situations are included in the annexes
Annex A: example of typology method
Annex B: default data for case specific method
Annex C: default data for boiler cycling method
Annex E, F & G: calculation examples
Default data can be adjusted through a national annex. slide 24
25. More information More information and downloads: www.iee-cense.eu
