The critical radius of insulation refers to the radius at which the heat transfer rate through the insulation is maximized. In other words, it is the optimal thickness of the insulation that minimizes heat loss.

Given data:
- Inner diameter of the steel steam pipe (d1) = 10 cm
- Outer diameter of the steel steam pipe (d2) = 11 cm
- Thermal conductivity of the insulation (k) = 1 W/mK
- Convective heat transfer coefficient (h) = 8 W/m2K

To find the critical radius of insulation, we need to consider the heat transfer through the steel pipe (conduction) and the heat transfer from the outer surface of the insulation to the surrounding air (convection).

1. Heat transfer through the steel pipe:
The rate of heat transfer through the pipe can be calculated using the formula:

Q_conduction = (2πkL / ln(d2 / d1)) * (T1 - T2)

Where:
- Q_conduction is the rate of heat transfer through conduction
- k is the thermal conductivity of the insulation
- L is the length of the pipe
- d1 is the inner diameter of the pipe
- d2 is the outer diameter of the pipe
- T1 is the temperature of the inner surface of the pipe
- T2 is the temperature of the outer surface of the pipe

2. Heat transfer from the outer surface of the insulation to the surrounding air:
The rate of heat transfer through convection can be calculated using the formula:

Q_convection = h * A * (T2 - T_air)

Where:
- Q_convection is the rate of heat transfer through convection
- h is the convective heat transfer coefficient between the surface of the insulation and the surrounding air
- A is the surface area of the insulation
- T2 is the temperature of the outer surface of the insulation
- T_air is the temperature of the surrounding air

By equating the two heat transfer rates (Q_conduction = Q_convection), we can solve for the critical radius of insulation.

However, since the question asks for the critical radius of insulation, we need to consider the radius of the insulation layer itself. The total radius of the insulation layer can be calculated as:

R_total = (d2 - d1) / 2

In this case, the critical radius of insulation would be the radius at which the total radius of the insulation layer is equal to the critical radius. Therefore, we need to find the critical radius of insulation by subtracting the radius of the steel pipe from the total radius of the insulation layer.

Critical radius of insulation = R_total - R_pipe

Now, substituting the given values:

R_total = (11 cm - 10 cm) / 2 = 0.5 cm
R_pipe = 10 cm / 2 = 5 cm

Critical radius of insulation = 0.5 cm - 5 cm = -4.5 cm

The critical radius of insulation cannot be negative, so there seems to be an error in the calculations. Please recheck the given data and calculations to find the correct answer.