Refrigerant cycle apparatus having refrigerant leak detector used to control first and second shutoff valves

A refrigerant cycle apparatus configured to circulate a lower flammability refrigerant categorized in lower flammability refrigerants by ISO 817 in a refrigerant circuit, the refrigerant cycle apparatus comprising:

• a first shutoff valve provided on a first side of a first portion of the refrigerant circuit and a second shutoff valve provided on a second side of the first portion of the refrigerant circuit;
• a detector configured to detect refrigerant leakage from the first portion of the refrigerant circuit into a predetermined space;
• and
• a controller configured to bring each of the first shutoff valve and the second shutoff valve into a shutoff state when the detector detects refrigerant leakage into the predetermined space, to inhibit refrigerant leakage into the predetermined space;
• wherein
• each of the first shutoff valve and the second shutoff valve in the shutoff state has a shutoff leakage rate, measured as an air leakage rate when fluid is air at 20° C. and a differential pressure between upstream and downstream of each valve is 1 MPa, said shutoff leakage rate being
• more than 300 (cm3/min), and
• less than 300×R (cm3/min),
• in which
• R
• =
• (
• ρ
• md
• ×
• V
• md
• ×
• A
• d
• )
• ⁢
• /
• ⁢
• (
• C
• r
• ×
• (
• 2
• ×
• Δ
• ⁢
• ⁢
• P
• r
• ⁢
• /
• ⁢
• ρ
• 1
• ⁢
• rl
• )
• 0.5
• ×
• A
• v
• ×
• ρ
• 1
• ⁢
• rl
• +
• A
• v
• ×
• (
• 2
• ⁢
• /
• ⁢
• (
• λ
• +
• 1
• )
• )
• (
• (
• λ
• +
• 1
• )
• ⁢
• /
• ⁢
• 2
• ⁢
• (
• λ
• -
• 1
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• )
• ×
• (
• λ
• ×
• P
• 1
• ⁢
• r
• ×
• ρ
• 1
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• rg
• )
• 0.5
• )
• ,
• wherein
• Av is a valve clearance sectional area (m2) of each of the first shutoff valve and the second shutoff valve in the shutoff state,
• ρ1rl is a mass concentration (kg/m3) of a refrigerant in a liquid phase,
• ρ1rg is a mass concentration (kg/m3) of a refrigerant in a gas phase,
• P1r is an upstream refrigerant pressure (MPa) of each of the first shutoff valve and the second shutoff valve, as a refrigerant saturation pressure when maximum temperature outside a building is set to 55° C.,
• λ is a refrigerant specific heat ratio,
• ρmd is a mass concentration (kg/m3) of a gaseous mixture containing air and a refrigerant having reached a refrigerant tolerable average concentration in the predetermined space after refrigerant leakage into the predetermined space and passing a clearance of a door that partitions an area inside the predetermined space from an area outside the predetermined space,
• Vmd is a velocity (m/s) of the gaseous mixture containing air and the refrigerant having reached the refrigerant tolerable average concentration in the predetermined space after refrigerant leakage into the predetermined space and passing the clearance of the door partitioning into inside and outside the predetermined space,
• Ad is an area (m2) of the clearance of the door that partitions the area inside the predetermined space from the area outside the predetermined space,
• ΔPr is a pressure difference (Pa) between inside and outside a hole at a position where the refrigerant leaks, as a differential pressure between the refrigerant saturation pressure when the maximum temperature outside the building is set to 55° C. and an atmospheric pressure, and
• Cr is 0.6 as a refrigerant flow rate coefficient in a case where the refrigerant in the liquid phase passes the hole at the position where the refrigerant leaks.