Indoor unit of refrigeration apparatus

An indoor unit of a refrigeration apparatus comprising:

• a drain pan that:
• comprises four wall surfaces including a first wall surface, and
• has a quadrangle shape in a plan view;
• a heat exchanger disposed above the drain pan and through which a combustible refrigerant, having a larger specific gravity than air, flows;
• a fan that generates air flow to the heat exchanger;
• a gas sensor that detects refrigerant leakage;
• and
• a casing accommodating the drain pan, the heat exchanger, the fan, and the gas sensor, wherein
• the casing comprises:
• side plates, including a first side plate, that constitute side surfaces of an outer contour of the casing;
• a partition plate that divides an internal space surrounded by the side plates into a first chamber in which the drain pan is disposed and a second chamber in which the fan is disposed;
• and
• a blow-out port disposed in the first side plate,
• the first side plate faces the first wall surface of the drain pan,
• the wall surfaces of the drain pan other than the first wall surface are arranged along the side plates or the partition plate, and
• the gas sensor is disposed above the drain pan and satisfies
• L·W{C1·H1/Q+C2·H/(Q−C3·L·H{circumflex over ( )}(3/2))}≤90,
• where
• C1=0.0067,
• C2=0.01172,
• C3=0.000153,
• H is a height of the gas sensor from an upper end of the drain pan in [m],
• L is a length of the first wall surface of the drain pan in [m],
• W is a length of a wall surface of the drain pan intersecting with the first wall surface in [m],
• H1 is a depth of the drain pan in [m], and
• Q is a refrigerant leakage flow rate in [m3/s].