Simulation tools

This research analysed the annual thermal performance of different courtyard geometric configurations in Iraq. The research used simulation tools as this research method provides the opportunity to evaluate and determine the impact of various factors on building performance

in different scenarios without the limitations of field experiments (Almhafdy et al., 2013; Bahar

et al., 2013). Exploring previous literature shows that a large number of simulation tools, such as Envi-met, Energy Plus, IES-VE, TRNSYS and DesignBuilder, have been developed and

used in buildings simulation studies (IBPSA; Sousa, 2012; de Wilde et al., 2009). However,

the available simulation tools differ in their features and characteristics, such as their

availability, user interface, simulation equations and assumptions (Bahar et al., 2013; Sousa,

2012). This makes finding an appropriate simulation tool a critical issue in achieving the objectives of the research. This study aimed to use a simulation tool that considers and determines the interaction of the various explored factors in courtyards. To select an appropriate simulation tool for this purpose, this research conducted an intensive review to explore potentially useful simulation tools. Table 4. 2 lists fifteen recent studies showing the range of simulation tools that have been used to determine the thermal conditions of courtyards or similar spaces. It can be seen that previous studies used a range of simulation tools, which has included: Envi-met, Solene, ESP-r, DesignBuilder, EnergyPlus (Table 4. 2).

Table 4. 2. Simulation tools - literature review

The study Used simulation tool Justification

Ridha, 2017

ENVI-met

This tool is used to simulate microclimatic conditions of urban spaces, including courtyards. It depends on well-based physical and fluid dynamics rules and principles in considering the impact of wide-range factors of outdoor spaces, which are not offered by other similar simulation tools

Peron, De Maria, Spinazzè, & Mazzali, 2015

Taleghani, Kleerekoper, Tenpierik, & van den Dobbelsteen, 201)

Hedquist & Brazel, 2014 Berkovic et al., 2012

60 Krüger, Minella, & Rasia, 2011

Malekzadeh, 2009

Huttner, Bruse, & Dostal, 2008 Ali-Toudert & Mayer, 2006

Gobakis & Kolokotsa, 2017 Coupling (ESP-r) and

(ENVI-met)

Indoor space simulation tools assume generic outdoor climatic conditions. This has led to inaccurate results. Accordingly, some studies have worked on simulating local outdoor microclimatic conditions of the examined buildings to feed the indoor space simulation tools. Envi-met has been one of the typical tools to simulate outdoor microclimatic conditions. Programming languages have been used to develop algorithms that couple indoor/outdoor simulation models.

Morille, Musy, & Malys, 2016 Coupling Solene thermo-

radiative model and Saturne code model Malys, Musy, & Inard, 2015

Gros, Bozonnet, & Inard, 2014 Coupling Envi-BatE and

Solene

Peng & Yi, 2014 Coupling DesignBuilder

and Envi-met X. Yang, Zhao, Bruse, & Meng, 2012 Coupling Envi-met &

EnergyPlus

From these studies, it can be seen that simulation experiments were either conducted using one simulation tool, typically Envi-met, or through coupling two simulation tools. Regarding the latter approach, the purpose is to provide a high level of accuracy for the dynamic heat exchange and transfer between indoor and outdoor spaces. In this kind of simulation experiments, one tool is used to determine outdoor conditions and the other for indoor conditions. The outputs of each simulation tool are used as inputs for the other. Results are correlated to produce final conclusions. This simulation approach was not adopted by this research for two reasons. First, it requires in-depth programming skills to manage the correlation between two simulation tools which is beyond the resources of the current study. Second, this research did not focus on the correlations between the courtyard space and surrounding indoor spaces, but on the impact of courtyard geometry on microclimatic conditions. Accordingly, this research did require interacting simulations but using one simulation tool to determine each of its variables.

This study explored various simulation tools that can be used individually to serve its aim of determining the air temperature, air velocity, MRT, insolation and globe temperature in courtyards. This included Envi-met 4.2, DesignBuilder, IES-VE, EnergyPlus, Solene, and

ESP-r.The possibility of using these simulation tools for the current purposes was explored

through a review of previous studies and by contacting support teams of these simulation tools. The results of the exploration showed that the most appropriate tool to determine air temperature, air velocity and MRT in courtyards for this study is Envi-met 4.2. Alongside using Envi-met 4.2, this study used IES-VE to simulate the insolation level in courtyards. Based on the results of Envi-met 4.2 simulation, the research used an equation developed by previous literature to determine globe temperature depending on the air temperature, MRT and air

velocity (Moss, 2015):

Tg= (MRT + 2.35 × Ta × (Av)0.5_{)/ (1 + 2.35 × (Av)}0.5₎

Where:

Tg: Globe Temperature, Ta: Air temperature, Av: air velocity

This adopted approach by this study to conduct its simulation experiments is underpinned by the following exploration results:

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 DesignBuilder and IES-VE have been validated and widely used in simulation studies

(Almhafdy et al., 2013; Ferrante, 2016; Sousa, 2012; Taleb & Sharples, 2011). However, the exploration revealed that both tools are not appropriate for simulating the microclimatic conditions of courtyard spaces. They are both designed to simulate indoor spaces.

 EnergyPlus, Solene, and ESP-r allow custom-made simulation experiments. However, they are not suitable for this study because they require programming skills and in-depth knowledge of related physics which are both out of the available resources.

 Envi-met is a Computational Fluid Dynamics (CFD) simulation tool that simulates the interactions between building surfaces, air and natural elements in urban spaces, such as

streets, plazas and courtyards (Berardi, 2016; ENVI-MET, 2017). It depends on well-

based physical and fluid dynamics rules and principles in considering the impact of wide- range effective factors on outdoor spaces. Among the factors that it considers are longwave and shortwave radiation, air temperature, wind velocity, humidity and vegetation

(Hedquist & Brazel, 2014; Malekzadeh, 2009), which are not comprehensively considered

by other similar simulation tools (Taleghani et al., 2015). The software versions before

version 4.2 had a number of drawbacks, which included, primarily, the problem of determining heat storage in walls during the day-time and heat release during the night-

time, which had led to inaccurate results (Berkovic et al., 2012); (Hedquist & Brazel,

2014). However, this problem has been solved by improvements to the software over

recent years (Simon, 2016). Recent studies have validated its results by making

comparisons between software simulation outputs and real-life measurements (Hedquist

& Brazel, 2014; Nasrollahi et al., 2017; Ridha, 2017).

 The used versions of Envi-met does not include an option to measure the insolation level in courtyards. For this reason, this research used IES-VE simulation tool to determine this variable.

 Globe temperature was determined through an equation as it is not possible to be determined directly by the explored simulation tools