*2.2.1 Test room description*

The building used for the experimental campaign belongs to the *Instituto de Investigacion Tecnologica* within the *Escuela Politecnica Superior de Algeciras* and is located at the Algeciras University Campus of the University of Cadiz (Spain). An external view of the building is shown in **Figure 5**. The building is an educational facility dedicated mainly to work spaces, offices and meeting rooms. The internal spaces in the building are conditioned by a variable refrigerant volume (VRV) cooling system, placed on the top of Wall 1 (see **Figure 5**). The dimensions of the room were W = 2.92 m width, L = 4.22 m length and H = 2.80 m height (**Figure 5b**). Its external wall, which was partially underground, contained an operable window. The ceiling was a concrete slab with suspended ceiling modules. A standard door is

Finally, the main objective of this research is the development of a methodology for the calibration of CFD models for rooms existing buildings from experimental results. This methodology can be used by other researchers to calibrate CFD models in existing rooms and then carry out detailed studies of temperature distribution, comfort and energy demand analysis. In addition, different conditioning systems, or different boundary conditions, can be tested, and the comfort or energy demand effect can be studied. The methodology is demonstrated by reproducing the experimental results measured in a mechanically cooled test room using CFD model. The calibration analysis is focused on a 2D plane of the room that was perpendicular to

the HVAC discharge outlet, where 12 temperature sensors where deployed (**Figure 1**). The variable of interest was the sensor air temperatures, measured at a steady-state regime in order to be compared with the CFD results. The boundary conditions of the CFD model were taken based on the measurements in the test room (i.e. surface temperatures, air velocity and air temperature of the HVAC

CFD is today one of the most accurate tools to predict the movement of air within an internal enclosure. CFD simulations require adequate computational power in order to solve the governing equations the fluid flows. It is also of a paramount importance that in order to get reliable results, a validation procedure based on trusted experimental data should be performed. A mesh verification is also necessary to achieve a good agreement between model accuracy and

In this work, a validation methodology for CFD models that combine natural and forced convection heat and flow transfer using experimental results is proposed. The validation steps and necessary parameters are described in the workflow shown in **Figure 2**. The diagram is divided into two parts, the left part represents the experimental test and the right part of the workflow represents the CFD model. The proposed method involves using the experimental boundary conditions set up at the room test as CFD model inputs. The variables used to feed the CFD models were (1) HVAC outlet air velocity, (2) HVAC air outlet temperature and (3) surface temperatures. The surface temperatures (3) were taken from the experimental test when steady-state condition was reached and were used as imposed inputs at the

The validation process starts with the design of the experiment, consisting of room preparation, air temperature sensors and surface temperature sensor placement (see **Figures 1** and **3**) and definition of case studies (see **Table 1**). In parallel, building geometry is introduced in the CFD tool. For every case study, the HAVC temperature and fan velocity are fixed. These values are used as boundary condition for the CFD model. During the experimental campaign, air temperatures and surface temperatures are collected, until the steady-state conditions are reached (see **Figure 4**). This process finalises with surface temperatures to feed the boundary conditions of the CFD model and air temperatures to be compared with the simulation ones. On the CFD side, once all boundary conditions have been introduced, simulations are performed keeping mesh goodness and convergence criteria (see sections 4.3 and 4.4). Previous air temperature measurements are compared with CFD model results. If the differences are larger than the own sensor accuracy error, the input parameters (1) and (2) are adjusted. This last step needs to be repeated

discharge outlet, etc.).

computational cost.

**6**

**2. Materials and methods**

*Computational Fluid Dynamics Simulations*

**2.1 Calibration methodology**

internal surfaces of the CFD model.

**Figure 3.** *Location of temperature sensors in the experimental office room.*


located on the wall opposite the window, contained a H = 2.1 m and W = 0.72 m standard door. The two internal walls separated the room from the adjacent offices and the internal corridor, with similar ventilation characteristics. During the experiment, the room was empty, without any furniture or occupants. **Figure 3** shows the location of the vertical strings with sensors and the internal HAVC split unit. Also in

*CFD isotherm contour map and sensor measurements in red points. Experiment 1 (a), 2 (b), 3(c) and 4(d).*

*Calibration Methodology for CFD Models of Rooms and Buildings with Mechanical Ventilation…*

*DOI: http://dx.doi.org/10.5772/intechopen.89848*

**Figure 4.**

**Figure 5.**

**9**

*Floor plan of the investigated office room.*

#### **Table 1.**

*Chronogram of the experiments campaign.*

*Calibration Methodology for CFD Models of Rooms and Buildings with Mechanical Ventilation… DOI: http://dx.doi.org/10.5772/intechopen.89848*

**Figure 4.**

*CFD isotherm contour map and sensor measurements in red points. Experiment 1 (a), 2 (b), 3(c) and 4(d).*

**Figure 5.** *Floor plan of the investigated office room.*

located on the wall opposite the window, contained a H = 2.1 m and W = 0.72 m standard door. The two internal walls separated the room from the adjacent offices and the internal corridor, with similar ventilation characteristics. During the experiment, the room was empty, without any furniture or occupants. **Figure 3** shows the location of the vertical strings with sensors and the internal HAVC split unit. Also in

**Figure 3.**

**Table 1.**

**8**

*Chronogram of the experiments campaign.*

**Experiment number**

*Location of temperature sensors in the experimental office room.*

*Computational Fluid Dynamics Simulations*

**Date/start time Date/end time Boundary conditions**

1 09.07.2016/13:30 10.07.2016/10:00 • •

4 12.07.2016/12:00 13.07.2016/10:00 • •

2 10.07.2016/12:00 11.07.2016/10:00 • • 3 11.07.2016/12:00 12.07.2016/10:00 • •

**Wall 3 temperature**

**Low High Low**

**HVAC fan speed**

**High (2.7 m/s)**

**(2.2 m/s)**

the waiting room heater is installed to increase the temperature of Wall 3 and see its influence on the indoor air temperature.

Wall 3 remained nonconditioned, while for the high-temperature setting, the adjacent room was heated with a heater. It is also important to notice that the air direction in the unit was fixed in a vertical position with the intention of minimising the air turbulence and favouring the temperature stratification of the room air. Eventually, four different configurations were chosen to perform the experiments, which are summarised in **Table 1**, alongside the test chronogram. The ultimate intention of these four experiments was to achieve a high temperature difference in

*Calibration Methodology for CFD Models of Rooms and Buildings with Mechanical Ventilation…*

Under the test conditions described previously, and for each experiment, a set of air temperature and surface temperature were taken. These values were taken using 12 temperature sensors distributed in a square grid in the measurement plane, as shown in **Figures 1** and **6**. This plane was placed orthogonal to Wall 1 at the middle of the HVAC unit. **Figure 6** shows the exact locations of the sensors. One of these sensors (sensor 10) was purposely placed at the exit of the HVAC outlet to measure the air temperature at that point. The 2D measurement plane includes the walls and

the ceiling, where 21 surface temperature sensors were installed uniformly (**Figure 6**). The measurement results are used as boundary conditions of the CFD computational model. An additional temperature sensor (sensor 13) was located in the adjacent room in order to measure the air temperature when the heater was operating (experiments 3 and 4). These temperatures were taken at the specified time at the end of the experiments using surface temperature metres. As previously mentioned, the purpose of heating up the adjacent room was to heat Wall 3.

The experiments were carried out for 20 hours, as seen in **Table 1**, in order to achieve steady-state conditions inside the room. Air temperatures were measured every minute during each experiment, while the surface temperatures only were measured at the end of the experiments, once a steady-state condition was reached. The measurement of the air speed at the HVAC discharge outlet was also taken at the end of each experiment (the fan's setpoint air speed was constant during the

The computational domain is a three-dimensional enclosure, and the used mesh type was a nonstructured mesh formed with tetrahedral cells. To develop the CFD simulation, the commercial software ANSYS CFX v.17 [1] was used. The model

*Vertical view of the measurement plane containing the superficial sensor (blue) and air sensors (red) location.*

the air of the test room.

*DOI: http://dx.doi.org/10.5772/intechopen.89848*

experiments).

**Figure 6.**

**11**

**2.3 Computational model**
