Calculate values of heat flux emitted by overhead pipeline segment (surrounded by air) as a function of construction, operation, and technical condition specifications according to Appendix 5.1 of Minenergo Method 278.

This type of calculations is usually made on design stage of district heating network (where water is a heat carrier) and is closely related to building codes and regulations.

```
m278hlair(
t1 = 110,
t2 = 60,
t0 = 5,
insd1 = 0.1,
insd2 = insd1,
d1 = 0.25,
d2 = d1,
lambda1 = 0.09,
lambda2 = 0.07,
k1 = 1,
k2 = k1,
lambda0 = 26,
len = 1,
duration = 1
)
```

- t1
temperature of heat carrier (water) inside the supplying pipe, [

*°C*]. Type:`assert_double`

.- t2
temperature of heat carrier (water) inside the returning pipe, [

*°C*]. Type:`assert_double`

.- t0
temperature of environment, [

*°C*]. In case of overhead laying this is the ambient temperature. Type:`assert_double`

.- insd1
thickness of the insulator which covers the supplying pipe, [

*m*]. Type:`assert_double`

.- insd2
thickness of the insulator which covers the returning pipe, [

*m*]. Type:`assert_double`

.- d1
external diameter of supplying pipe, [

*m*]. Type:`assert_double`

.- d2
external diameter of returning pipe, [

*m*]. Type:`assert_double`

.- lambda1
thermal conductivity of insulator which covers the supplying pipe [

*W/m/°C*]. Type:`assert_double`

.- lambda2
thermal conductivity of insulator which covers the returning pipe [

*W/m/°C*].`assert_double`

.- k1
technical condition factor for insulator of supplying pipe, []. Type:

`assert_double`

.- k2
technical condition factor for insulator of returning pipe, []. Type:

`assert_double`

.- lambda0
thermal conductivity of environment, [

*W/m/°C*]. In case of overhead laying this is the thermal conductivity of open air. Type:`assert_double`

.- len
length of pipeline segment, [

*m*]. Type:`assert_double`

.- duration
duration of heat flux emittance, [

*hour*]. Type:`assert_double`

.

Heat flux emitted by pipeline segment during `duration`

, [*kcal*].
If `len`

of pipeline segment is 1 *m* and `duration`

of
heat flux emittance is set to 1 *hour* then the return value is equal
to that in [*kcal/m/h*] units and so comparable with values of
heat flux listed in

Minenergo Order 325.
Type: `assert_double`

.

Details on using `k1`

and `k2`

are the same as for
`m278hlcha`

.

Other Minenergo:
`m278hlcha()`

,
`m278hlund()`

,
`m278insdata`

,
`m278inshcm()`

,
`m278soildata`

,
`m325beta()`

,
`m325dropt()`

,
`m325nhldata`

,
`m325nhl()`

,
`m325testbench`

```
m278hlair()
#> [1] 138.7736
# [1] 138.7736
```