Simulation In Control System Sensor Location Design - ibpsa

More documents

Recommendations

Info

Proceedings of Building Simulation 2011:12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November.Software ESP-rDynamic simulation software ESP-r has been usedfor analysis of location of the sensor . Computerprogramme ESP-r (Environmental SystemsPerformance - research) is environment of dynamicsimulation for analysis of mass flows and heat flowsin buildings. In the course of the simulation theevolution of mass flows and energy flows duringchanges in regulatory intervention and limitingconditions (outdoor microclimate and operatingindoor conditions) is monitored. At every time stepof simulation a problem is limited to steady flows(ESP-r manual, 1998).ModelFor purposes of analysis of the influence of thesensor location (for measuring indoor temperature)onto the heating system control and energyperformance of offices, two reference rooms, whichdiffer from each other in isolation of external wallswere selected. The office "A225" was additionallyinsulated by VIP panels (λ = 0,017 W/m.K) frominside the external wall, according to reality. Theroom "A226" is kept in original condition withoutinsulation. These offices are situated in an existingbuilding of the Faculty of Civil Engineering CTU inPrague. The rooms are located in a sixteen-storeythree-tract building with active heating andventilation without air conditioning.Figure 1. Model of part the office building withmarking the reference rooms - the programme ESP-rThe evaluated office rooms are 5 m x 3 m in size andthe ceiling height is 3.3 m. Both rooms have oneexternal wall with a window a size 3 m x 1.6 m,floor, ceiling, interior wall separating the room fromthe corridor, the partitions between the offices andthe hall door. Because the offices are on the secondfloor, heat losses by transmission are expected tooccur only through the perimeter wall. The facade isoriented toward the southwest.Proposed working hours in the office building are inthe working days from 8:00 a.m. to 5:00 p.m.For heating to a temperature of 21 °C, theperformance of the heating elements available are inthe range of 0 - 4000 W. This performance isdesigned to cover the heat needs and to ensure therequirements of the indoor environment in theextreme cases in the Czech climatic conditions. Heatenergy is distributed by 25 % radiation and 75%convection. Heating is controlled according to indoortemperature. The heating system is workingpermanently (it was established on the basis ofprevious measurements) also during not-workinghours and on weekends and holidays. Humidity is notcontrolled in either of the rooms "A225" and "A226"(Kabrhel et al., 2011).Table 1Heat transfer coefficient of different constructions.BUILDING STRUCTUREU VALUE[W/m 2 .K]Perimeter wall without insulation A226 0,68Perimeter wall with insulation A225 0,15Window 4,10 !Floor 0,85Ceiling 0,85Indoor wall 2,56Partition wall 2,00Door 3,50Ventilation is forced, with a fixed fresh air changerate. Supposed the intensity of air exchange during aworking time differs according to nominal occupancyof the room. In the office "A225" the intensity of airexchange is set at 100 m 3 /h (2 persons in a room) andin office "A226" the intensity of air exchange is50 m 3 /h. The intensity of air exchange decreasesoutside the normal working hours to 20 m 3 /h (in alloffices). Infiltration of old windows results inconsiderable proportion of the ventilation, it provides1,5 times the air exchange.To determine the indoor gains should be consideredduring model building operation. The model reckonswith the presence of one or two people in the officeduring working hours. Office facilities (computers,printers, etc.) should also be reckoned with.Computers and printers are the biggest producers ofindoor heat gains. Lighting operates during workinghours throughout the year (illumination intensity is500 lux) (Bartoňová,Kabele,2011).Table 2Determination of indoor heat gainSOURCE OF HEAT GAIN VALUEPerson150 W/personComputer set (PC and printer)250 WLighting 35W/m 2- 2574 -
]C[TemperatureProceedings of Building Simulation 2011:12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November.Verification of the modelTo verify the model functionality, it was necessary toperform the verification model on the basis of themeasurements. Measurements were carried out in thewinter 2010 as a part of student assignment.. Thismeasurement consisted of outdoor air temperature,humidity, solar radiation intensity, speed and winddirection and indoor air temperature in the referenceroom (office "A226"). Unfortunately, it was notpossible to measure operative temperature at thattime due to technical and operational circumstances(the room was occupied and cooperation with userwas not the best). It was necessary to acceptassumption that in case that the simulated results ofindoor air temperature will match the measuredvalues, it is possible to expect that there is no majormistake in the model.Figure 2 Comparison of the measured and in themodel used outdoor air temperatureMeasured outdoor temperatures were used as input tothe model. Due to differences between measurementtime steps and that required by the model,interpolation was required. The comparison is shownin Figure 2.22.021.821.621.421.221.020.820.620.420.220.0Indoor Air Temperature(15.12.2010)Measured Indoor TemperatureTimeIndoor Temperature of ESP -rFigure 3 Comparison of the indoor air temperaturewith measured valuesFigure 3 shows that the program ESP-r expected tomaintain the desired indoor temperature, but in factthere was a decrease or increase in temperature.Actually, the measured temperature rose and fell inthe range of ±0.2 °C around the temperature selectedin simulation programme. This difference wasevaluated as acceptable and model in the airtemperature domain has been considered assatisfactory.SimulationIn the next step, the work continued with thesimulation. The question to be solved at this pointwas how to deal with the limited possibilities of ESPrin terms of operative temperature calculation andrequirement for more detailed view on thetemperature distribution in the room to get data forthe next experiments and decisions related to optimalsensor placement.ESP-r enables to calculate operative (in the programcalled resulting) temperature t o in one point, which islocated in the ideal centre of the room. This value issufficient for building energy performancecalculations, but not for our task, where we wanted toinvestigate non-uniformity of the operativetemperature within the room. To simulate this, weused the MRT (mean radiant temperature, t MRT )module of ESP-r (Kabele, Krtková, 2001). Thismodule enables to simulate MRT in selected and bycoordinates specified positions of the room. Theproblem is that MRT gives information only aboutsurface temperatures “visible” from a given point andno information about operative temperature, which isdefined as “a uniform temperature of a radiantlyblack enclosure in which an occupant wouldexchange the same amount of heat by radiation plusconvection as in the actual non-uniform airtemperature” . To get operative temperature indifferent points of the room, we used the basicdefinition of operative temperature expressed byequation (1):to=( h ⋅t+ h ⋅t)cacrh + hrMRT[ °C](1)According to (Government regulation 523, 2002) forair movement velocities in the room up to 0.2 m/s itis possible to simplify the equation (1) into equation(2), based on assumption, that within low airvelocities, convective and radiant heat transfercoefficients are equal:t( t + t )a MRTo=2[ ° C](2)- 2575 -
Page 4 and 5: Proceedings of Building Simulation
Page 6: Proceedings of Building Simulation

Simulation In Control System Sensor Location Design - ibpsa

Create successful ePaper yourself

Delete template?

Save as template?