An assembly comprising a thermal management device for promoting the maintenance of a temperature within a predetermined range, in an inner space and/or vis-à-vis an element disposed therein, said assembly comprising: - said inner space, - said device arranged around the inner space and placed in an outdoor environment exposed to a non-constant temperature, the device comprising at least one thermal insulating element and, from inside, where is located said inner space and/or the element disposed therein, towards outside where said outdoor environment is located: -- an inner thermal-storage element containing at least one phase change material having a phase transition temperature between liquid and solid, which is different from temperatures included in said predetermined temperature range and/or substantially equal to the temperature of a charge fluid, -- and an outer thermal barrier containing at least one phase change material which stores or releases thermal energy by phase transitions between liquid and solid, and which has at least a phase transition temperature of between -50°C and 50°C, in order to slow down, by phase transitions, the thermal action of the outdoor environment, - and fluid supplying means (21,35,4,46,47) for temporarily supplying said charge fluid, at least at a temperature different from temperatures in said predetermined temperature range, in thermal transfer with said at least one phase change material of the inner thermal-storage element such that it stores thermal energy, being characterized in that: - the thermal insulating element is interposed between the thermal barrier and the inner thermal-storage element, and - temporarily supplied in said inner space by the fluid supplying means (21,35,4,46,47), the charge fluid is in thermal exchange therein with said at least one phase change material. - said inner space, - said device arranged around the inner space and placed in an outdoor environment exposed to a non-constant temperature, the device comprising at least one thermal insulating element and, from inside, where is located said inner space and/or the element disposed therein, towards outside where said outdoor environment is located: -- an inner thermal-storage element containing at least one phase change material having a phase transition temperature between liquid and solid, which is different from temperatures included in said predetermined temperature range and/or substantially equal to the temperature of a charge fluid, -- and an outer thermal barrier containing at least one phase change material which stores or releases thermal energy by phase transitions between liquid and solid, and which has at least a phase transition temperature of between -50°C and 50°C, in order to slow down, by phase transitions, the thermal action of the outdoor environment, -- an inner thermal-storage element containing at least one phase change material having a phase transition temperature between liquid and solid, which is different from temperatures included in said predetermined temperature range and/or substantially equal to the temperature of a charge fluid, -- and an outer thermal barrier containing at least one phase change material which stores or releases thermal energy by phase transitions between liquid and solid, and which has at least a phase transition temperature of between -50°C and 50°C, in order to slow down, by phase transitions, the thermal action of the outdoor environment, - and fluid supplying means (21,35,4,46,47) for temporarily supplying said charge fluid, at least at a temperature different from temperatures in said predetermined temperature range, in thermal transfer with said at least one phase change material of the inner thermal-storage element such that it stores thermal energy, - the thermal insulating element is interposed between the thermal barrier and the inner thermal-storage element, and - temporarily supplied in said inner space by the fluid supplying means (21,35,4,46,47), the charge fluid is in thermal exchange therein with said at least one phase change material.