Relaciones de Gestión de la Seguridad con variables personales y empresariales

The following rules are set by ASHRAE to calculate the cooling load for each component of lights, people and applications. However, to adopt the ASHRAE calculations, Iranian regular practice for these calculations have also been applied (FINE HVAC 14).

1. Calculate 24 h profile of component heat gains for design day (for conduction, first account for conduction time delay by applying conduction time series).

2. Split heat gains into radiant and convective parts using radiant and convective parts. 3. Apply appropriate radiant time series to radiant part of heat gains to account for time delay in conversion to cooling load.

4. Sum convective part of heat gain and delayed radiant part of heat gain to determine cooling load for each hour for each cooling load component.

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5.7.1 Lighting

Occupied spaces are affected by heat gains from electric lighting. The amount of heat is directly dependent on illumination level and the efficiency of the light source (Brown and Dekay 2001, p.42). The radiation energy emitted from a lamp will result in a heat gain to the space only after it has been absorbed by the room surfaces. According to the Iranian national housing census (2010) the average use of fluorescent lightings are 6.1 hours a day for each household.

Q-l

= (W * 3.412) * Fu * Fs * CLF-h (sensible heat gain)

Q-l = Sensible Heat Gain (SHG) from lights

W = Lighting power output in Watts (Btu/hr = W * 3.412)

FU = Usage factor or percentage of maximum design for each hour of the day Fs = Service Allowance Factor or Multiplier

CLF-h = Cooling Load Factor (CLF) for given hour. This depends on zone type, total hours that lights are on, and number of hours after lights are turned on.

However, when the lighting specifications are not known the following equation is applied: W = K × A

Where;

A =Area

K =Lighting density =3 W/ft2 (for residential buildings)

As a result, the assigned lighting gains for the base-case is assumed to be 32.3 W/m2

5.7.2 Occupants

One of the important factors in heat load calculation is the “people” load. As a rule of thumb, one can use 400Btuh/person for internal heat gains. However Iranian sources (Davoodi, 2012) recommended the following heat gain to be applied (Table 5.8).

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Table 5.8 – People Internal Gain

Heat generated by people

Application Sensible Latent Total(Btuh)

Home and theatre 200 250 450

Iranian sources suggested the following equation to calculate the heat gains from people;

𝑄_{𝑡𝑜𝑡𝑎𝑙} = 𝑄_𝑝∗ 𝐶𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡

Where;

Qp = heat gains from people = 450Btuh (including sensible and latent heat gains) Coefficient = 0.5

450 * 0.5 = 225Btuh = 65W

5.7.3 Household and Appliances

Iranian national housing census statistics shows that on average most of the household equipment is used for less than 10 hours a month. The following Table (5.9) shows the most effective equipment that runs for more than 10 hours a month in Iranian dwellings.

Table 5.9 – Heat Gains by Appliances

Heat generated by equipment

Total(Btuh) Operation time (daily)

Cooking oven 3500 2.2h

TV (32”) 340 3.8h

5.7.4 Occupancy Set Points

According to municipality statistics (2008), only 21% of women are employed, while over 82% of men are employed. As a result the majority of residential buildings in Tehran are occupied all day round. This occupancy means that the cooling and heating systems are required to be operative all the time as long as the thermal comfort temperature is met. However, this type of occupancy affects the heat gains from people as during the weekdays and school time, it is assumed that one person is at home.

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5.7.5 Heating and Cooling Set Points

Although Iranian building codes recommended a setting point of 20oC in the winter and 28oC in the summer, it is required that buildings are equipped with a thermostat to control the internal temperature. Likewise, the base case, is not equipped with thermostats, therefore, the temperature set points in simulation was worked out according to the average set point temperature Tehran according to the national housing census (2010). The census states that while the majority of residents are not aware of the internal temperature, the internal temperature in winter is on average 23oC and in the summer 26oC.

5.7.6 Natural Ventilation Settings

The main natural ventilation inlet in residential buildings in Tehran is through the windows. It is almost impossible to assume the exact window opening time and the degree of the openings. However, for this study, it was assumed that according to Iranian building code recommendations, windows would be open when the external temperatures are between 20oC and 25oC. The degree of opening for the base case was assigned as 50% as the window type is centre-hung. The opening time was also assigned all day round when the mentioned external temperature is met.

5.7.7 Infiltration Rate (ACH)

Infiltration rate is one of the most important factors to predict the energy performance of buildings. One of the main reasons for this importance is the heat loss and gains through the infiltrations are comparable with heat transfer through a well or poor insulated envelope (O’Brien, 2010). This means that the estimation of model infiltrations is of great significance. However, this can only be identified accurately by applying a blower door test (ASHRAE, 2005). This can be applied after the construction has been completed.

For this study, the infiltration rate was assigned as a fixed rate based on the average Iranian new built building infiltration rates are around 0.70 ach (Zomorodian, 2015). However this rate for old buildings increases up to three times (Zomorodian, 2015).

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5.7.8 Orientation

Building regulations in Iran state that only 60% of the site can be built on and the remaining area (40%) must be used as courtyard. Courtyards must be located on the southern side of south-north orientated sites and on the eastern side of sites orientated east-west. These rules intend to maximize the solar energy through the wide windows that are open to through the wide windows that are open to the courtyard. Therefore, some houses are east-facing but the majority face south (Nasrolahi, 2009). For this reason, only south-north typology has been selected for evaluation in this research.

5.7.9 Floor selection

Household location of the simulation was set at the middle floor, as opposed to the top- or bottommost floors. In addition, majority of units are located in the middle floors (floors between top and bottom floor) therefore this study focuses on the majority floors that are expressed middle floor or intermediate floors. Households other than the target were blocked in general under the same set temperature to create conditions similar to the actual conditions for the target household in relation to the outer environment.