SIST EN 15377-3:2007
Heating systems in buildings - Design of embedded water based surface heating and cooling systems - Part 3: Optimizing for use of renewable energy sources
Heating systems in buildings - Design of embedded water based surface heating and cooling systems - Part 3: Optimizing for use of renewable energy sources
This document is applicable to water based surface heating and cooling systems in residential, commercial and industrial buildings.
The methods apply to systems integrated into the wall, floor or ceiling construction without any open air gaps.
The methods do not apply to heated or chilled ceiling panels or beams.
This standard is part 3 of a series of standards:
- Part 1: Steady-state calculation methods for determination of the heating and cooling capacity;
- Part 2: Method for design, dimensioning and installation;
- Part 3:Optimizing for use of renewable energy sources.
The aim of the present Standard is to give a guide for the design to promote the use of renewable energy sources and to provide a method for the use of Thermo-Active-Building-Systems (TABS).
The method allows calculation of peak cooling capacity of a thermo-active system, based on heat gains (solar, internal loads, ventilation).
This method also allows calculation of the energy demand on the water side (system) to be used for sizing of the cooling system, e.g. chiller, fluid flow rate.
Steady state heating capacity is calculated according to method B or E of prEN 15377-1 (part 1 of this series of standards).
Heizungssysteme in Gebäuden - Planung von eingebetteten Flächenheiz- und kühlsystemen mit Wasser als Arbeitsmedium - Teil 3: Optimierung für die Nutzung erneuerbarer Energiequellen
Dieses Dokument gilt für Flächenheiz- und kühlsysteme mit Wasser als Arbeitsmedium in Wohnhäusern, Geschäfts- und Industriebauten.
Die Verfahren gelten für in Wand-, Decken- oder Fußbodenkonstruktionen eingebaute Systeme ohne offene Luftspalte.
Die Verfahren gelten nicht für beheizte oder gekühlte Deckenplatten oder strahler.
Diese Norm ist Teil 3 einer Reihe von Normen, die folgende Teile umfasst:
- Teil 1: Berechnungsverfahren zur Bestimmung der Heiz- und Kühlleistung im Beharrungszustand;
- Teil 2: Verfahren zur Planung, Auslegung und Installation;
- Teil 3: Optimierung für die Nutzung erneuerbarer Energiequellen.
Das Ziel der vorliegenden Norm besteht darin, einen Leitfaden für die Planung der Nutzung erneuerbarer Energiequellen und zum Einsatz von thermoaktiven Bauteilsystemen (TABS) zur Verfügung zu stellen.
Dieses Werkzeug ermöglicht die Berechnung der Spitzenkühlleistung eines thermoaktiven Systems auf der Basis der (solaren und durch interne Lasten oder die Lüftung verursachten) Wärmegewinne.
Dieses Verfahren ermöglicht auch die Berechnung des Energiebedarfs auf der Wasserseite (System), der für die Dimensionierung des Kühlsystems, wie z. B. des Wasserkühlers, des Flüssigkeitsstroms usw., verwendet wird.
Die Heizleistung unter den Bedingungen des Beharrungszustandes wird nach Verfahren B oder E berechnet, siehe Teil 1 dieser Normenreihe.
Für die Anwendung der vorliegenden Norm sind folgende Normen erforderlich: prEN 15377 1, prEN WI 16, prEN WI 17 und prEN WI 31 (siehe 2).
Durch die Anwendung der vorliegenden Norm lassen sich Eingangsdaten für die Anwendung der folgenden Normen ermitteln: prEN WI 12, Raumtemperatur-, Last- und Energieberechnungen für mit Klimaanlagen ausgestattete Gebäude und prEN WI 28, Wärmetechnisches Verhalten von Gebäuden — Berechnung von sommerlichen Raumtemperaturen bei Gebäuden ohne mechanische Kühlung — Vereinfachtes Berechnungsverfahren.
Conception des systemes de chauffage et refroidissement par le sol, le mur et le plafond - Partie 3 : Optimisation pour l'usage des sources d'énergie renouvelable
Ce document s’applique aux systèmes de chauffage et de refroidissement de surfaces à eau dans les bâtiments résidentiels, commerciaux et industriels.
Les méthodes s’appliquent aux systèmes intégrés dans la construction des murs, du plancher ou du plafond sans aucune poche d’air ouverte.
Elles ne s’appliquent pas, en revanche, aux panneaux ou poutres de plafond chauffés ou réfrigérés.
La présente norme est la troisième partie d’une série de normes :
Partie 1 : Détermination de la puissance calorifique et frigorifique de conception ;
Partie 2 : Conception, dimensionnement et installation ;
Partie 3 : Optimisation de l’utilisation des énergies renouvelables.
La présente norme vise à fournir un guide pour une conception promouvant le recours à des sources d’énergie renouvelables et à proposer une méthode pour l’utilisation de systèmes d’éléments de construction thermoactifs (TABS).
La méthode permet de calculer la puissance frigorifique de pointe d’un système thermoactif sur la base des apports de chaleur (solaire, charges internes, ventilation).
Elle permet également de calculer la demande d’énergie côté eau (système) à utiliser pour le dimensionnement du système de refroidissement (par exemple, refroidisseur, débit du fluide, etc.).
La puissance calorifique en régime permanent est calculée selon la méthode B ou E du prEN 15377-1 (Partie 1 de cette série de normes).
Grelni sistemi v stavbah - Načrtovanje vodnih sistemov za ogrevanje in hlajenje, vgrajenih v gradbeno konstrukcijo - 3. del: Optimizacija rabe obnovljivih energijskih virov
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Heating systems in buildings - Design of embedded water based surface heating and cooling systems - Part 3: Optimizing for use of renewable energy sourcesRYOMLYLKConception des systemes de chauffage et refroidissement par le sol, le mur et le plafond - Partie 3 : Optimisation pour l'usage des sources d'énergie renouvelableHeizungssysteme in Gebäuden - Planung von eingebetteten Flächenheiz- und kühlsystemen mit Wasser als Arbeitsmedium - Teil 3: Optimierung für die Nutzung erneuerbarer EnergiequellenTa slovenski standard je istoveten z:EN 15377-3:2007SIST EN 15377-3:2007en,de91.140.10Sistemi centralnega ogrevanjaCentral heating systemsICS:SLOVENSKI
STANDARDSIST EN 15377-3:200701-december-2007
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 15377-3October 2007ICS 91.140.10 English VersionHeating systems in buildings - Design of embedded water basedsurface heating and cooling systems - Part 3: Optimizing for useof renewable energy sourcesConception des systèmes de chauffage et refroidissementpar le sol, le mur et le plafond - Partie 3 : Optimisation pourl'usage des sources d'énergie renouvelableHeizungsanlagen in Gebäuden - Planung von eingebettetenFlächenheiz- und -kühlsystemen mit Wasser alsArbeitsmedium - Teil 3: Optimierung für die Nutzungerneuerbarer EnergiequellenThis European Standard was approved by CEN on 18 August 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 15377-3:2007: E
EN 15377-3:2007 (E) 2 Contents Page Foreword.3 Introduction.5 1 Scope.6 2 Normative references.6 3 Terms, definitions and symbols.6 3.1 Data referred to the circuit:.7 3.2 Data referred to the room geometry and the boundary conditions:.7 3.3 Data referred to the slab and its partitions:.8 3.4 Data referred to the initial temperature profile.8 3.5 Calculation of the temperature profile and the heat fluxes in the generic time-step n.9 4 Relation to other EPBD standards.9 5 Optimisation of systems for facilitating the use of renewable energy sources.9 6 The concept of Thermo-Active-Building-Systems (TABS).11 7 Calculation methods.16 7.1 General.16 7.2 Rough sizing method.16 7.3 Simplified sizing method using diagrams.16 7.4 Simplified model based on finite difference method (FDM).23 7.4.1 Cooling system.23 7.4.2 Hydraulic circuit.23 7.4.3 Slab.23 7.4.4 Room.23 7.4.5 Limits of the method.25 7.5 Dynamic building simulations program.26 8 Input for computer simulations of energy performance.26 Annex A
(informative)
Simplified diagrams.27 Annex B
(normative)
Calculation method.31 B.1 Pipes level.31 B.2 Subdivision of the slab.31 B.3 Choice of the calculation time step:.35 B.4 Calculations for the generic n-th time step.35 B.5 Sizing of the system.38 Annex C
(informative)
Tutorial guide for assessing the model.39 Annex D
(informative)
Computer program.43 Bibliography.72
EN 15377-3:2007 (E) 3 Foreword This document (EN 15377-3:2007) has been prepared by Technical Committee CEN/TC 228 “Heating systems in buildings”, the secretariat of which is held by DS. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by April 2008, and conflicting national standards shall be withdrawn at the latest by April 2008. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association (Mandate M/343), and supports essential requirements of EU Directive 2002/91/EC on the energy performance of buildings (EPBD). It forms part of a series of standards aimed at European harmonisation of the methodology for calculation of the energy performance of buildings. An overview of the whole set of standards is given in prCEN/TR 15615. The subjects covered by CEN/TC 228 are the following: - design of heating systems (water based, electrical etc.); - installation of heating systems; - commissioning of heating systems; - instructions for operation, maintenance and use of heating systems; - methods for calculation of the design heat loss and heat loads; - methods for calculation of the energy performance of heating systems. Heating systems also include the effect of attached systems such as hot water production systems. All these standards are systems standards, i.e. they are based on requirements addressed to the system as a whole and not dealing with requirements to the products within the system.
Where possible, reference is made to other European or International Standards, a.o. product standards. However, use of products complying with relevant product standards is no guarantee of compliance with the system requirements. The requirements are mainly expressed as functional requirements, i.e. requirements dealing with the function of the system and not specifying shape, material, dimensions or the like.
The guidelines describe ways to meet the requirements, but other ways to fulfil the functional requirements might be used if fulfilment can be proved. Heating systems differ among the member countries due to climate, traditions and national regulations. In some cases requirements are given as classes so national or individual needs may be accommodated. In cases where the standards contradict with national regulations, the latter should be followed. prEN 15377 Heating systems in buildings – Design of embedded water based surface heating and cooling systems consists of the following parts: Part 1: Determination of the design heating and cooling capacity Part 2: Design, dimensioning and installation Part 3: Optimizing for use of renewable energy sources
EN 15377-3:2007 (E) 4 According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EN 15377-3:2007 (E) 5 Introduction The aim of the present standard is to give a guide for the design of water based embedded heating and cooling systems to promote the use of renewable energy sources and to provide a method for actively integrating the building mass to reduce peak loads, transfer heating/cooling loads to off-peak time periods and to decrease systems size.
A section in the present standard describes how the design and dimensioning can be improved to facilitate renewable energy sources. Peak loads can be reduced by activating the building mass using pipes embedded in the main concrete structure of the building (Thermo-Active-Building-Systems, TABS). For this type of systems, the steady state calculation of heating and cooling capacity (part 1 of this standard) is not sufficient. Thus, several sections of this standard describe methods for taken into account the dynamic behavior. The proposed methods are used to calculate and verify that the cooling capacity of the system is sufficient and to calculate the cooling requirements on the water side for sizing the cooling system. The energetic assessment of surface heating and cooling systems may also be carried out according to national guidelines accomplishing the goal of this standard.
EN 15377-3:2007 (E) 6 1 Scope This document is applicable to water based surface heating and cooling systems in residential, commercial and industrial buildings. The methods apply to systems integrated into the wall, floor or ceiling construction without any open air gaps. The methods do not apply to heated or chilled ceiling panels or beams. This standard is part 3 of a series of standards: Part 1: Determination of the design heating and cooling capacity; Part 2: Design, dimensioning and installation; Part 3:Optimizing for use of renewable energy sources. The aim of the present standard is to give a guide for the design to promote the use of renewable energy sources and to provide a method for the use of Thermo-Active-Building-Systems (TABS).
The method allows calculation of peak cooling capacity of a thermo-active system, based on heat gains (solar, internal loads, ventilation). This method also allows calculation of the energy demand on the water side (system) to be used for sizing of the cooling system, e.g. chiller, fluid flow rate. Steady state heating capacity is calculated according to method B or E of prEN 15377-1 (part 1 of this series of standards). 2 Normative references The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 15251, Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics EN 15255, Thermal performance of buildings – Sensible room cooling load calculation – General criteria and validation procedures EN 15265, Energy performance of buildings - Calculation of energy needs for space heating and cooling using dynamic methods - General criteria and validation procedures prEN 15377-1:2005, Heating systems in buildings – Design of embedded water based surface heating and cooling systems — Part 1: Determination of the design heating and cooling capacity prEN 15377-2, Heating systems in buildings — Design of embedded water based surface heating and cooling systems — Part 2: Design, dimensioning and installation 3 Terms, definitions and symbols For the purposes of this document, the terms and definitions given in prEN 15377-1:2005 and the following symbols apply.
EN 15377-3:2007 (E) 7 3.1 Data referred to the circuit: spHm,& specific water flow, calculated on the area covered by the circuit
kg/ (m2 s) ; cw specific heat capacity of the water
J/ (kg K) ; T pipe spacing m ; da
external diameter of the pipe
m ; sr
thickness of the pipe wall
m ; rλ thermal conductivity of the material of the pipe wall
W/ (m K) ; AFloor area cooled/heated by the circuit m2 ; LR length of the circuit m ; MaxWP maximum cooling (<0) or heating (>0) power for a conditioning plant W ; 0wθ supply water temperature at the beginning of the simulation °C ; limwθ minimum (in the cooling case) or maximum (in the heating case) supply water temperature obtainable by the machine °C . 3.2 Data referred to the room geometry and the boundary conditions: AWalls overall area of vertical walls, external facade excluded m2 ; Fv Floor-Ext Wall view factor floor-external wall; Fv Floor-Ceiling view factor floor-ceiling; Fv Floor-Walls view factor floor-walls; Radd Floor additional resistance covering the upper side of the slab (m2 K)/W ; Radd Ceiling additional resistance covering the lower side of the slab (m2 K)/W ; RWalls resistance of the surface layer of internal walls (m2 K)/W ; hAir-Floor
convective heat transfer coefficient between the air and the floor W/(m2 K) ; hAir-Ceiling
convective heat transfer coefficient between the air and the ceiling W/(m2 K) ; hAir-Walls
convective heat transfer coefficient between the air and the internal walls W/(m2 K) ; hFloor-Walls
radiant heat transfer coefficient between the floor and the internal walls W/(m2 K) ; hFloor-Ceiling
radiant heat transfer coefficient between the floor and the ceiling W/(m2 K) ; hCeiling-Walls
radiant heat transfer coefficient between the ceiling and the internal walls W/(m2 K) ; CWalls average specific thermal inertia of the internal walls J/(m2 K)
t∆ calculation time step s . The following data shall be known for all the day, and the values during the n-th time step from the beginning of the simulation have to be defined:
EN 15377-3:2007 (E) 8 Tcomfort maximum operative temperature allowed for comfort conditions °C ; nSunQ& solar gain in the room in the present calculation time step W ; nTransmQ& incoming heat flux to the room from the external wall in the present calculation time step W ; nAirQ& convective heat flux extracted by the air circuit W ; nIntRadQ& internal radiant heat gain due to people or electrical equipment in the present calculation time step W ; nIntConvQ& internal convective heat gain due to people or electrical equipment in the present calculation time step W ; nrmf running mode (the value is 1 when the system is running and 0 when the system is switched off) dimensionless ; 3.3 Data referred to the slab and its partitions: s1
thickness of the upper part of the slab
m ; s2
thickness of the lower part of the slab
m ; J1 number of material layers constituting the upper part of the slab dimensionless ; J2 number of material layers constituting the lower part of the slab dimensionless ;
As a consequence, J=J1+J2 represents the total number of material layers constituting the slab and J sets of physical properties (ρj, cj, λj, δj, mj, Rj) shall be known or chosen, where: ρj density of the material constituting the j-th layer
kg/m3 ; cj specific heat capacity of the material constituting the j-th layer
J/ (kg K) ; λj thermal conductivity of the j-th layer W/ (m K) ; δj thickness of the j-th layer m ,
δj = 0 if the layer is a mere thermal resistance; mj number of partitions of the j-th layer
dimensionless ; Rj thermal resistance summarizing the j-th layer m2K/W ,
Rj > 0 if the layer is a mere thermal resistance. For geometrical consistency: 2112111sandsJJJjjJjj==∑∑+==δδ. 3.4 Data referred to the initial temperature profile The initial value of the supply water temperature (0wθ) and the interface temperatures of partitions of the slab (0i,Iθ withLii≤≤0) shall be decided. As for the slab, a possible choice could be assigning the same value to all the interfaces, equal to the mean temperature at the start of the simulation.
EN 15377-3:2007 (E) 9 However, if the simulation covers more than one running cycle, the choice of the initial values is not decisive. In fact, it will influence only the very first time steps of the simulation.
3.5 Calculation of the temperature profile and the heat fluxes in the generic time-step n The temperature reached at a certain interface at the end of the previous time step is used for calculation of the heat fluxes acting on the building structures and for calculation of the consequent temperatures at the end of the time step in progress. These magnitudes are: nConvq& global specific convective heat gains W/m2 ; nRadq& global specific radiant heat gains W/m2 ; nAirθ air temperature in the room in the present calculation time step °C ; nWallsθ mean temperature of the walls in the present calculation time step °C ; nOpθ operative temperature in the room in the present calculation time step °C ; 1−nwθ supply water temperature at the end of the previous time step °C ; 1−nexitwθ outlet water temperature at the end of the previous time step °C ;
1,−niIθ temperature of the i-th interface, with Lii≤≤0, at the end of the previous time step, °C ; The results obtained at every time step are: nwθ supply water temperature at the end of the time step in progress °C ;
nFθ, nsθ temperature of the upper and lower sides of the slab at the end of the time step in progress °C ; niI,θ temperature of the i-th interface, with Lii≤≤0, at the end of the time step in progress, °C . 4 Relation to other EPBD standards The present standard requires input from the following standards: prEN 15377-1, EN 15251, EN 15255 and EN 15265.
The present standard provides input data to the following standards: EN 15243 and EN ISO 13792. 5 Optimisation of systems for facilitating the use of renewable energy sources Transporting energy by water uses less auxiliary energy for pumps and less installation space than carrying the same amount of energy by air. A further optimizing is to use water at temperatures close to room temperature for heating and cooling: low temperature heating - high temperature cooling.
EN 15377-3:2007 (E) 10 For normal embedded radiant floor-, wall-, and ceiling heating/cooling systems, increasing the pipe spacing and decreasing the difference between supply and return water temperature results in water temperatures closer to room temperature, but this increases flow rates and pipe lengths leading to higher pressure losses. This forces designers to choose between either increasing auxiliary energy use for pumps or applying pipes with a larger diameter, both of which are undesirable options. This can partly be compensated by using more circuits of shorter pipe lengths. These factors shall be optimized according to prEN 15377-2 (part 2 of this series of standards).
For Thermo-Active-Building–Systems, a further optimization regarding use of renewable energy sources is made by reducing the peak load, transferring the load to off-peak time periods, downsizing of energy generation systems, and increased efficiency of energy generation due to water temperature level. This facilitates the possible use of energy sources such as solar collectors, ground source heat pumps, free cooling, ground source heat exchangers, aquifers.
EN 15377-3:2007 (E) 11
6 The concept of Thermo-Active-Building-Systems (TABS) A Thermo-Active-Building-System (TABS) is a water based heating and cooling system, where the pipes are embedded in the central concrete core of a building construction (see Figure 1). The heat transfer takes place between the water (pipes) and the concrete, between the concrete core and the surfaces to the room (ceiling, floor) and between the surfaces and the room.
Key W window
P pipes
R room
C concrete
F floor RI reinforcement Figure 1 – Thermo-active radiant system
EN 15377-3:2007 (E) 12 Looking at a typical structure of a thermo-active system, heat is removed by a cooling system (e.g. chiller, heat pump) connected to pipes embedded in the slab. The system can be divided into the following elements (see Figure 2):
where: PL = pipes level 1 = cooling system (machine) 2 = hydraulic circuit 3 = slab including core level with pipes 4 = possible additional resistances (floor covering or suspended ceiling) 5 = room below and room above Figure 2 – Simple scheme of a thermo-active system
EN 15377-3:2007 (E) 13 Peak-shaving is the possibility to heat and cool the structures of the building during a period in which the occupants may be absent (e.g. during night time), reducing also the peak of the required power (see Figure 3). In this way, energy consumption may be reduced and a lower night time electricity rate (if obtainable) can be exploited, and furthermore, downsizing of the cooling system, including the chiller, is possible.
Key 1 heat gain X-axis time of the day 2 power needed for conditioning the ventilation air Y-axis cooling power 3 power needed on the water side 4 peak of the required power reduction
Figure 3 – Example of peak-shaving effect
TABS may be used both with natural and mechanical ventilation (depending on weather conditions). Mechanical ventilation with dehumidifying may be required depending on external climate and indoor humidity production. In the example in Figure 3, the required cooling power needed for dehumidifying the air during day time is sufficient for cooling the slab during night time. The designer needs to know if the capacity at a given water temperature is sufficient to keep the room temperature in a given range. The designer needs also to know the heat flow on the water side to be able to dimension the heat distribution system and the chiller/boiler. The present document provides methods for this. Some detailed building-systems calculation models have been developed, e.g. for determination of the heat exchanges under non-steady state conditions in a single room, for determination of thermal and hygrometric balance of the room air, for prediction of comfort conditions, for checking of condensation on surfaces, for availability of control strategies and for calculation of the incoming solar radiation. The use of such detailed calculation models is, however, limited due to the high amount of time needed for the simulations. Development of a more user-friendly tool is required. Such a tool is provided in the following, which allows simulation of thermo-active systems in an easy way. Internal temperature changes only moderately during the day, and the aim of a good design of TABS is to maintain comfort during the day within the range of comfort, i.e. –0,5 < PMV < 0,5, according to EN 15251 (see Figure 4).
EN 15377-3:2007 (E) 14
Key θmr mean radiant temperature X-axis time of the day θair air temperature Y-axis, left temperature °C θf floor temperature Y-axis, right PMV values θc ceiling temperature θw exit return water temperature PMV Predicted Mean Vote Figure 4 – Example of temperature profiles
The diagram in Figure 5 show an example of the relation between internal heat gains, water supply temperature, heat transfer on the room side, hours of operation and heat transfer on the water side. The diagrams correspond to a concrete slab with raised floor (R=0,45 m2K/W) and a permissible room temperature range of 21 °C to 26 °C. The upper diagram shows on the y-axis the maximum permissible total heat gain in the space (internal gains plus solar gains) in W/m2, and on the x-axis the required water supply temperature in °C. The lines in the diagram correspond to different hours of operation (8 h, 12 h, 16 h, 24 h) and different maximum amounts of energy supplied in Wh/m2 per day. The lower diagram shows the cooling power in W/m2 required on the water side (for dimensioning of the chiller) for thermo-active slabs as a function of supply water temperature and operation time. Further, the amount of energy rejected per day is indicated in Wh/m2 per day. The example shows, that by a maximum internal heat gain of 38 W/m2 and 8 h operation, a supply water temperature of 18,2 °C is required. If, instead, the system is in operation for 12 h, a supply water temperature of 19,3 °C is required. In total, the amount of energy rejected from the room is appr. 335 Wh/m2 per day. The required cooling power on the water side is by 8 h operation 37 W/m2 and by 12 h operation only 25 W/m2. Thus, by 12 h operation, the size of the chiller can be reduced significantly. The total heat rejection on the water side is appr. 300 Wh/m2 per day.
EN 15377-3:2007 (E) 15
Key A =Maximum total heat gain in space [W/m2 floor area] B = Maximum C = Minimum O&E = occupants and equipment (acc. to SWKI 95-3) L = lighting (acc. to SWKI 95-3) D =Mean cooling power tabs [W/m2 floor area] Figure 5 – Working principle of TABS
EN 15377-3:2007 (E) 16 7 Calculation methods
7.1 General The following calculation methods can be applied: rough sizing method based on a standard calculation of the cooling load (accuracy 20-30%). To be used based on the knowledge of the peak value for heat gains, see 7.2;
simplified sizing method using diagrams based on 24 one-hour values of the heat gains (accuracy 15-20%), see 7.3; simplified model based on finite difference method, FDM, (accuracy 10-15%). Detailed dynamic simulation for the thermal conduction in the slab via FDM, based on 24 one-hour values of the variable cooling loads of the room as well as the temperatures of the air, see 7.4;
detailed simulation models (accuracy 6-10%). Overall dynamic simulation model for the radiant system and the room, see 7.5.
7.2 Rough sizing method The cooling system shall be sized for 70 % of the peak cooling load (EN 15255, prEN 15377-1 and prEN 15377-2). In this case, calculation of the cooling load has to be carried out using an operative temperature of 24 °C. 7.3 Simplified sizing method using diagrams In this case, calculation of the heat gains has to be carried out by means of 24 hourly calculations with an operative temperature of 24 °C. If heat gains are approximated, 10 % of the solar gain has to be added each hour in order to take into account the gains due to external windows. This method is based on the assumption that the entire conductive slab is at a constant temperature during the whole day. This average temperature of the slab is calculated by the method itself and is related to the supply water temperature of the running time of the circuit. The following data and parameters are involved by this method: Q, which is the specific daily heat load on the room during the design day in kWh/m2 per day. It is the sum of the above mentioned 24 one-hour values of the heat gains divided by the floor area. The pattern of the load profile shall be known; comfort: maximum operative temperature allowed for comfort conditions
°C; Exposure of the room, in order to determine when the peak load from heat gains occurs: East (morning), South (noon) or West (afternoon); Number of active surfaces. in order to distinguish whether the slab works by heat transfer both on the floor side and on the ceiling side or only on the ceiling side (see Figure 6); h: number of hours of fluid flow through the circui
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