## About Galistan

Galinstan is a eutectic alloy composed of gallium, indium, and tin (hence its name, which is derived from the gallium, indium, and stannum, the Latin name for tin). Galistan melts at −19 °C (−2 °F) and is thus liquid at room temperature.

### Summary

Name | Galistan |

Phase at STP | liquid |

Density | 6440 kg/m3 |

Ultimate Tensile Strength | N/A |

Yield Strength | N/A |

Young’s Modulus of Elasticity | N/A |

Brinell Hardness | N/A |

Melting Point | -19 °C |

Thermal Conductivity | 16.5 W/mK |

Heat Capacity | 296 J/g K |

Price | 700 $/kg |

## Density of Galistan

In words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is **kilograms per cubic meter** (**kg/m ^{3}**). The Standard English unit is

**pounds mass per cubic foot**(

**lbm/ft**).

^{3}Density of Galistan is **6440 kg/m ^{3}.**

### Example: Density

Calculate the height of a cube made of Galistan, which weighs one metric ton.

**Solution:**

**Density** is defined as the **mass per unit volume**. It is mathematically defined as mass divided by volume: **ρ = m/V**

As the volume of a cube is the third power of its sides (V = a^{3}), the height of this cube can be calculated:

The height of this cube is then **a = 0.537 m**.

### Density of Materials

## Thermal Properties of Galistan

### Galistan – Melting Point

**Melting point of Galistan is -19 ****°C**.

Note that, these points are associated with the standard atmospheric pressure. In general, **melting** is a **phase change** of a substance from the solid to the liquid phase. The **melting point** of a substance is the temperature at which this phase change occurs. The **melting point **also defines a condition in which the solid and liquid can exist in equilibrium. For various chemical compounds and alloys, it is difficult to define the melting point, since they are usually a mixture of various chemical elements.

### Galistan – Thermal Conductivity

Thermal conductivity of Galistan is **16.5** **W/(m·K)**.

The heat transfer characteristics of a solid material are measured by a property called the **thermal conductivity**, k (or λ), measured in **W/m.K**. It is a measure of a substance’s ability to transfer heat through a material by conduction. Note that **Fourier’s law** applies for all matter, regardless of its state (solid, liquid, or gas), therefore, it is also defined for liquids and gases.

The **thermal conductivity** of most liquids and solids varies with temperature. For vapors, it also depends upon pressure. In general:

Most materials are very nearly homogeneous, therefore we can usually write ** k = k (T)**. Similar definitions are associated with thermal conductivities in the y- and z-directions (ky, kz), but for an isotropic material the thermal conductivity is independent of the direction of transfer, kx = ky = kz = k.

### Galistan – Specific Heat

**Specific heat of Galistan is 296**** J/g K**.

**Specific heat, or specific heat capacity, **is a property related to** internal energy** that is very important in thermodynamics. The **intensive properties c_{v}** and

**are defined for pure, simple compressible substances as partial derivatives of the**

*c*_{p}**internal energy**and

*u(T, v)***enthalpy**, respectively:

*h(T, p)*where the subscripts **v** and **p** denote the variables held fixed during differentiation. The properties **c _{v} **and

**c**are referred to as

_{p}**specific heats**(or

**heat capacities**) because under certain special conditions they relate the temperature change of a system to the amount of energy added by heat transfer. Their SI units are

**J/kg K**or

**J/mol K**.

### Example: Heat transfer calculation

Thermal conductivity is defined as the amount of heat (in watts) transferred through a square area of material of given thickness (in metres) due to a difference in temperature. The lower the thermal conductivity of the material the greater the material’s ability to resist heat transfer.

Calculate the rate of __heat flux__ through a wall 3 m x 10 m in area (A = 30 m^{2}). The wall is 15 cm thick (L_{1}) and it is made of Galistan with the __thermal conductivity__ of k_{1} = 16.5 W/m.K (poor thermal insulator). Assume that, the indoor and the outdoor __temperatures__ are 22°C and -8°C, and the __convection heat transfer coefficients__ on the inner and the outer sides are h_{1} = 10 W/m^{2}K and h_{2} = 30 W/m^{2}K, respectively. Note that, these convection coefficients strongly depend especially on ambient and interior conditions (wind, humidity, etc.).

Calculate the heat flux (**heat loss**) through this wall.

**Solution:**

As was written, many of the heat transfer processes involve composite systems and even involve a combination of both __conduction__ and __convection__. With these composite systems, it is often convenient to work with an__ overall heat transfer coefficient__**, **known as a **U-factor**. The U-factor is defined by an expression analogous to **Newton’s law of cooling**:

The **overall heat transfer coefficient** is related to the total thermal resistance and depends on the geometry of the problem.

Assuming one-dimensional heat transfer through the plane wall and disregarding radiation, the **overall heat transfer coefficient** can be calculated as:

The **overall heat transfer coefficient **is then: U = 1 / (1/10 + 0.15/16.5 + 1/30) = 7.02 W/m^{2}K

The heat flux can be then calculated simply as: q = 7.02 [W/m^{2}K] x 30 [K] = 210.64 W/m^{2}

The total heat loss through this wall will be: **q _{loss} **= q . A = 210.64 [W/m

^{2}] x 30 [m

^{2}] =

**6319.15 W**