Riederer, Peter (2002) Thermal room modelling adapted to the test of hvac control systems. PhD thesis Energétique, CENERG- Centre d'Energétique, ENSMP p.189.
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Abstract
Room models, currently used for controller tests, assume the room air to be perfectly mixed. A new room model is developed, assuming non-homogeneous room conditions and distinguishing between different sensor positions.
From measurement in real test rooms and detailed CFD simulations, a list of convective phenomena is obtained that has to be considered in the development of a model for a room equipped with different HVAC systems.
The zonal modelling approach that divides the room air into several sub-volumes is chosen, since it is able to represent the important convective phenomena imposed on the HVAC system. The convective room model is divided into two parts: a zonal model, representing the air at the occupant zone and a second model, providing the conditions at typical sensor positions. Using this approach, the comfort conditions at the occupant zone can be evaluated as well as the impact of different sensor positions.
The model is validated for a test room equipped with different HVAC systems. Sensitivity analysis is carried out on the main parameters of the model.
Performance assessment and energy consumption are then compared for different sensor positions in a room equipped with different HVAC systems. The results are also compared with those obtained when a well-mixed model is used.
A main conclusion of these tests is, that the differences obtained, when changing the position of the controller's sensor, is a function of the HVAC system and controller type. The differences are generally small in terms of thermal comfort but significant in terms of overall energy consumption.
For different HVAC systems the cases are listed, in which the use of a simplified model is not recommended.
| Item Type: | PhD Thesis (PhD) |
|---|---|
| Thesis Supervisor: | Marchio, Dominique and Knabe, Gottfried |
| Date: | 02 January 2002 |
| Board of examiners: | Adnot, Jérôme and Dexter, Arthur and Gruber, Peter and Inard, Christian and Knabe, Gottfried and Visier, Jean-Christophe and Marchio, Dominique |
| Discipline: | Energétique |
| Collection (Fonds): | ENSMP |
| Institution: | ENSMP |
| Department: | CENERG- Centre d'Energétique |
| Subjects: | 5. Fluid Mechanics and Energy |
| Uncontrolled Keywords: | HVAC control, Emulation, Simulation, Room model, Zonal model, Sensor position, Convective room phenomena, Performance assessment of room controllers, Energy consumption, Graphical programming, Régulation de température, Simulation, Modèle de zone, Modèle zonal, Position du capteur, Phénomènes convectifs, Performance d'un régulateur, Consommation d'énergie, Environnement graphique, Regelung, Simulation, Raummodell, Zonenmodell, Sensorposition, Konvektion, Regelungsqualität, Energieverbrauch, graphische Programmierung |
Table of content
TABLE OF CONTENTS
TABLE OF CONTENTS - 15
LIST OF SYMBOLS - 1
INTRODUCTION - 5
CHAPTER I - CONTEXT AND OBJECTIVES - 7
1. INTRODUCTION TO HVAC BUILDING CONTROL - 8
2. TEST OF HVAC CONTROLLERS - 10
2.1 Test of HVAC terminal controllers - 10
2.2 Test of HVAC building controllers - 11
2.3 Real test environment for controller tests - 12
2.4 Use of virtual laboratories for the test of controllers - 12
2.4.1 Principle of a virtual laboratory - 12
2.4.2 Criteria of manufacturers for virtual laboratories - 13
2.4.3 Application of a virtual laboratory to controller tests - 14
2.4.4 Rules for the development of a virtual laboratory - 16
3. MAIN OBJECTIVE AND WORK PLAN OF THE PHD THESIS - 17
4. CONCLUSION CHAPTER 1 - 18
CHAPTER II - ANALYSIS OF PHENOMENA IN A HEATED, COOLED OR AIRCONDITIONED ROOM - 19
1. GENERAL AIRFLOW PATTERNS IN ROOMS - 20
2. DESCRIPTION OF TEST CELL AND MEASUREMENT DEVICES - 23
2.1 The test room - 23
2.2 Emitters and gains in the test room - 24
2.3 Measurement of surface temperatures - 25
2.4 Tools for the evaluation of convective phenomena in the test room - 25
2.4.1 Measurement of air temperatures (quantitative tool) - 25
2.4.2 CFD simulation of air temperatures (qualitative tool) - 26
3. ANALYSIS OF ZONE CONDITIONS - STEADY STATE PHENOMENA - 27
3.1 Observed airflow patterns - 27
3.2 Conditions at the occupants zone - 29
3.2.1 Horizontal temperature profile - 29
3.2.2 Vertical temperature profile - 31
3.3 Conditions at sensor zones - 33
3.3.1 Positioning of temperature sensors - 33
3.3.2 Room without convective heat sources - 35
3.3.3 Air distribution at ceiling - heating systems - 36
3.3.4 Air distribution at floor - cooling systems - 36
3.4 Study of flow around a controller sensor - 38
3.4.1 Study on 3-d effects of the flow in sensor zones - 38
3.4.2 Study of the flow in the negatively buoyant wall jet for the example of heating systems - 42
3.5 Conclusion on steady state phenomena - 44
4. ANALYSIS IN TRANSIENT CONDITIONS - 45
4.1 General transient phenomena - 45
4.2 Measurement of transient phenomena - 45
4.2.1 Switching on - 45
4.2.2 Switching off - 47
4.3 Conclusion transient phenomena - 48
5. CONCLUSION CHAPTER II - 49
CHAPTER III - ANALYSIS OF EXISTING ROOM MODELS AND DEFINITION OF CRITERIA FOR A NEW MODEL - 51
1. CRITERIA OF A NEW ZONE MODEL - 52
1.1 General criteria for the model - 52
1.1.1 Optimised detail of room model - 52
1.1.2 Use of available and simple model parameters - 53
1.1.3 Validity of the model - 53
1.2 Criteria regarding Test of controllers - 53
1.2.1 Link between actuator/emitter and room - 54
1.2.2 Link between the room and the controller - 54
1.2.2.1 Position of the controller sensor in the room - 54
1.2.2.2 Measurement of a controller sensor - 55
1.2.2.3 Conclusion on necessary outputs for sensor measurement - 57
1.2.3 Link between the room conditions and performance assessment - 57
1.2.3.1 Position of performance assessment - 57
1.2.3.2 State variable(s) or index for performance assessment - 58
1.2.3.3 Conclusion on performance assessment - 63
2. ANALYSIS OF EXISTING ROOM MODELS - 65
2.1 Models of convection - 66
2.1.1 Well-mixed mode66
2.1.2 Computational fluid models - 66
2.1.3 Zonal models - 67
2.1.4 Simplified models using supplementary identification or correlation - 71
2.2 Models of 71
2.3 Models of radiation - 72
2.4 Lumped parameter room models - 72
2.5 Conclusion on room models - 73
2.6 Conclusion on model criteria - 74
3. CONCLUSION CHAPTER III - 76
CHAPTER IV - MODEL DEVELOPMENT - 77
1. SYSTEM DEFINITION AND GENERAL EQUATIONS OF THE CONVECTIVE ROOM MODEL - 78
2. DIVISION OF THE ROOM INTO SUB-VOLUMES - 79
3. STUDY AND SELECTION OF CORRELATIONS FOR CONVECTIVE PH81
3.1 Airflow in pl 81
3.1.1 Radiator plumes - 81
3.1.2 Convector plumes 82
3.1.3 Free plumes - 83
3.1.4 General representation for plumes - 84
3.2 Airflow in jets - 84
3.2.1 Overview and 84
3.2.2 Isothermal jets - 86
3.2.2.1 Jet zones and centre-line jet velocity - 86
3.2.2.2 Velocity profile - 87
3.2.2.3 Air flow rates - 88
3.2.3 Non isothermal jets - 89
3.2.3.1 Horizontal jets - 89
3.2.3.2 Vertical j89
3.2.4 General representation for jets - 91
3.3 Airflow at internal wall surfaces - 92
3.3.1 Natural convectio93
3.3.2 Negatively buoyant flow - 94
3.4 Convective heat transfer coefficients at the internal room surfaces - 96
3.5 Conclusion on correlations - 97
4. DEVELOPMENT OF THE CONVECTIVE ROOM MODEL - 97
4.1 Division of the sub-volumes in two parts - 98
4.2 Development of the simplified zonal model - 99
4.2.1 General structure of the model - 99
4.2.2 Definition of the particular air flow matrices - 99
4.2.2.1 Air flow due to emitter plume or positively buoyant fan coil unit jet - 99
4.2.2.2 Air flow due to negatively buoyant fan coil unit jet - 100
4.2.2.3 Air flow in the ceiling jet - 101
4.2.2.4 Air flow due to plumes from internal heat gains - 101
4.2.2.5 Air flow due to the boundary layer at the external surfaces - 102
4.2.2.6 Air flow due to a boundary layer of natural convection at the internal walls - 102
4.2.2.7 Air flow due to negatively or positively buoyant air flow at the internal walls - 103
4.2.2.8 Air exchange with external conditions or the HVAC system - 104
4.2.3 Construction of the final air flow matrix AFM - 104
4.2.4 Estimation of the maximum downward travel of negatively buoyant air flow at the internal walls - 104
4.2.5 Calculation of heat transfer in the zonal model - 105
4.3 Development of a Module estimating the temperature in the sensor zones - 106
4.3.1 Division of the sensor zones into three characteristic zones - 106
4.3.2 Function for the temperature in the transition zone of the wall jet - 106
4.3.3 Calculation of the temperature in the sensor zones - 107
4.4 Conclusion model development - 110
5. IMPLEMENTATION OF THE ROOM MODEL IN THE GRAPHICAL SIMULATION ENVIRONMENT - 110
5.1 First level: the Room model - 111
5.2 Model of 113
5.2.1 The zonal model 113
5.2.1.1 State space representation - 113
5.2.1.2 Sub-volumes with high and low inertia - 114
5.2.2 The sensor mod116
5.3 Conclusion model implementation - 118
6. EXPERIMENTAL VALIDATION OF THE ROOM MODEL - 119
6.1 Case 1: Electric convector - 120
6.2 Case 2: Fan coil unit in heating mode - 124
6.3 Case 3: Fan coil unit in cooling mode - 128
6.4 Conclusion on validation of the room model - 132
7. SENSITIVITY ANALYSIS ON IMPORTANT PARAMETERS OF THE ROOM MODEL - 132
7.1 Sensitivity of the correlation for penetration of the negatively buoyant air flow at the internal walls133
7.1.1 Error of air flow entrained into the jet or plume - 133
7.1.2 Error of air entrainment into the plume or jet at the ceiling - 133
7.1.3 Error due to the estimation of the length of the wall jet - 133
7.1.4 Error introduced by the estimation of the initial jet thickness - 133
7.1.5 Error due to a false temperature difference between the air temperature in the wall jet and at the centre 134
7.1.6 Addition of errors - 134
7.2 Sensitivity of the sensor module on an error in the important parameters of the wall jet correlation137
8. CONCLUSION CHAPTER IV - 138
CHAPTER V - APPLICATIONS - 139
1. SIMULATION OF A BUILDING - 140
1.1 Building structure - 140
1.1.1 Building level - 140
1.1.2 Room level - 141
1.2 Building HVAC equipment and design - 141
1.2.1 Electric convector - 142
1.2.2 Fan coil unit - 142
1.2.3 VAV system - 142
1.2.3.1 Diffuser selection - 142
1.2.3.2 The VAV control system - 144
1.2.3.3 VAV terminal box - 144
1.2.4 Controllers - 145
1.2.5 Controller sensor145
2. SINGLE ROOM TESTS - 146
2.1 Electric con 147
2.1.1 General behaviour of resultant temperature - 147
2.1.2 Possible impact on results of controller tests - 148
2.2 Fan coil unit - 150
2.2.1 Heating tests - 150
2.2.1.1 General behaviour of resultant temperature - 150
2.2.1.2 Possible impact on results of controller tests - 151
2.2.2 Cooling tests - 153
2.2.2.1 General behaviour of resultant temperature - 153
2.2.2.2 Possible impact on results of controller tests - 154
2.2.2.3 Emitted power and water flow rate through the coil - 156
2.3 VAV system - 157
2.3.1 Cooling tests - 157
2.3.1.1 Slot dif157
2.3.1.2 Radial ceiling diffuser - 161
2.3.2 Heating tests - 164
2.3.2.1 Slot dif164
2.3.2.2 Radial ceiling diffuser - 168
3. VAV WHOLE BUILDING PERFORMANCE TESTS - 172
3.1 Impact of room model and sensor position on the performance assessment - 172
3.1.1 Summer case - 172
3.1.2 Winter case - 174
3.2 Impact of room model and sensor position on building energy consumption - 176
4. IMPACT OF SENSOR POSITION AND ROOM MODEL ON THE TUNING OF CONTROLLERS - 177
5. CONCLUSION CHAPTER V - 179
CONC181
REFERENCES - 183
| ID Code: | 632 |
|---|---|
| Deposited By: | Peter RIEDERER |
| Deposited On: | 31 March 2004 |
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