gistfile1.py

import sys

class R(object):
    outer_wall = 15
    inner_wall = 1.5
    ceiling = 50
    floor = 20

class T(object):
    """Design temperatures"""
    indoor = 72
    outdoor = 25

class Surface(object):
    def __init__(self, area, r):
        self.area = area
        self.r = r

    @property
    def u(self):
        return 1.0/self.r

    @property
    def delta_t(self):
        return self.indoor_temp - self.outdoor_temp

    @property
    def heatloss(self):
        return self.area * self.u * self.delta_t


S = Surface

S.outer_walls = S(10*10*2, R.outer_wall)
S.inner_walls = S(10*10*2, R.inner_wall)
S.ceiling = S(10*10, R.ceiling)
S.floor = S(10*10, R.floor)

S.outer_walls.outdoor_temp = T.outdoor
S.ceiling.outdoor_temp = T.outdoor
S.floor.outdoor_temp = T.outdoor
S.inner_walls.outdoor_temp = T.indoor

air_volume = 10*10*10.0
air_temp = T.indoor

fan_cfm = 50

air_temp_over_time = []
seconds = 3600
for x in range(seconds):
    cf_new_air = fan_cfm/60.0
    cf_old_air = air_volume - cf_new_air
    air_temp = (cf_old_air/air_volume)*air_temp + (cf_new_air/air_volume)*T.indoor

    S.outer_walls.indoor_temp = \
    S.ceiling.indoor_temp = \
    S.floor.indoor_temp = \
    S.inner_walls.indoor_temp = air_temp

    heat_loss_to_outdoors = (S.outer_walls.heatloss + S.ceiling.heatloss + S.floor.heatloss) / 3600.0
    heat_loss_to_indoors = S.inner_walls.heatloss / 3600.0

    heat_loss = heat_loss_to_outdoors + heat_loss_to_indoors
    heat_loss_in_cf_degrees = heat_loss/0.018
    heat_loss_in_degrees = heat_loss_in_cf_degrees / air_volume
    air_temp -= heat_loss_in_degrees

    if '--print' in sys.argv:
        print "heat loss from outer walls:", S.outer_walls.heatloss
        print "heat loss from floor:", S.floor.heatloss
        print "heat loss from ceiling:", S.ceiling.heatloss
        print "heat loss from outdoors:", heat_loss_to_outdoors
        print "heat gain from indoors:", -heat_loss_to_indoors
        print "room temp change:", -heat_loss_in_degrees
        print "room temp:", air_temp
    air_temp_over_time.append(air_temp)

if '--plot' in sys.argv:
    from pylab import arange, array, plot, show
    x = arange(0, seconds)
    y = array(air_temp_over_time)
    plot(x, y)
    show()