Method for regulating the temperature of the storage chamber for products of an indirect injection vehicle transporting heat-sensitive products

Abstract

The invention relates to a method for transporting heat-sensitive products in a refrigerated lorry of the indirect injection type, wherein the temperature T.sub.int inside the storage chamber is regulated by varying the pinch of the exchanger (Pinch=T.sub.int−TFluid outflow) according to the position of the internal temperature T.sub.int in relation to a temperature set value.

Claims

1. A method for transporting heat-sensitive products in a refrigerated truck, of a type in which the truck is provided: with at least one product storage chamber, with a reservoir of a cryogenic fluid, with a heat exchanger system internal to said at least one chamber, through which system the cryogenic fluid circulates, with an air circulation system, able to bring an air internal to the chamber into contact with cold walls of the heat exchanger system, with temperature sensors able to determine the temperature of an atmosphere internal to said at least one chamber (T.sub.int) and that of cold vapors leaving the heat exchangers system (T.sub.fluid outlet) and with a control and management unit able to regulate the internal temperature T.sub.int to a reference value T.sub.ref by ordering a closing or opening, or a degree of such opening/closing, of one or more valves supplying the heat exchanger system with cryogenic fluid; characterized in that the temperature T.sub.int is regulated by implementing the following measures: the following parameters are determined in real time: a) ΔT=T.sub.int −T.sub.ref; and b) a value of a Pinch of the heat exchanger system, where: Pinch =T.sub.int −T.sub.fluid outlet ; and a parameter P, which is a function of ΔT, is taken into consideration and the control and management unit, as long as the Pinch is below or equal to the parameter P, commands the holding open or increased opening of the valve or valves used to supply the heat exchanger system with cryogenic fluid.

2. The method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein when the Pinch rises above the parameter P, the control and management unit orders the partial or full closure or a reduction in the opening of the valves depending on where the temperature within the chamber lies in relation to a reference, and within a pull down phase or a hold phase.

3. The method for transporting heat-sensitive products in a refrigerated truck of claim 2, wherein the or each of the valves supplying the heat exchanger system with cryogen are of an “all-or-nothing” type and the control and management unit therefore commands the full closing of this or these valves when the Pinch rises above the parameter P.

4. The method for transporting heat-sensitive products in a refrigerated truck of claim 2, wherein the or each of the valves supplying the heat exchanger system with cryogen are of a proportional valve type and the control and management unit therefore commands, when the Pinch rises above the parameter P, the partial or full closure or a reduction in the opening of this or these valves according to where the temperature within the chamber lies in relation to a reference, and within a pull down phase or a hold phase.

5. The method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the or each of the valves supplying the heat exchanger system with cryogen are of , an “all-or-nothing” type, and the control and management unit then commands the full opening of this or these valves as long as the Pinch is below or equal to the parameter P.

6. The method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the or each of the valves supplying the heat exchanger system with cryogen are of a proportional valve type and the control and management unit then commands, according to where the temperature within the chamber lies in relation to a reference, and within a pull down phase or a hold phase.

7. The method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the parameter P is expressed as a function of ΔT using a formula in the form: $\begin{array}{cc}P=a1n(1+\mathrm{abs}\left(\Delta T\right)+b& \left(\mathrm{Equation}1\right)\end{array}$ where “In” is a naperian logarithm function, and “abs” is an absolute value function.

8. The method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the parameter P is expressed as a function of ΔT in a formula of the form: $\begin{array}{cc}P=\mathrm{aln}\left(1+\mathrm{abs}\left(\Delta T\right)\right)+\left(b\times T_{\mathrm{ref}}+c\right)\times \mathrm{abs}\left(\Delta T\right)+d& \left(\mathrm{Equation}2\right)\end{array}$ where “In” is a naperian logarithm function, and “abs” is an absolute value function.

9. The method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the parameter P is expressed as a function of ΔT in a formulation of the form: $\begin{array}{cc}P=\left(a\times \mathrm{abs}\left(\Delta T\right)+b\right)\times e^{\frac{-1}{1+{\mathrm{abs}\left(\Delta T\right)}^2}}+\left(c\times \mathrm{abs}\left(\Delta T\right)+d\right)\times e^{-\mathrm{abs}\left(\Delta T\right)}& \left(\mathrm{Equation}3\right)\end{array}$ where “abs” is an absolute value function and “e” is an exponential function.

10. A method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the cryogenic fluid is liquid nitrogen.

11. A method for transporting heat-sensitive products in a refrigerated truck of claim 1, wherein the air circulation system is a blower type.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further, the attached FIGS. 1, 2 and 3 will provide a clear understanding of the benefit reaped by such regulation according to equation 3:

(2) FIG. 1 represents the change in temperature internal to the chamber

(3) T.sub.int (curve x)) and of the exchanger outlet temperature T.sub.outlet according to the prior art (regulations currently performed: fixed pinch=curve y)) and according to the invention (variable pinch, curve z)).

(4) FIG. 2 depicts the two temperature-drop curves obtained in the chamber, using the regulations currently employed (curve m)) and according to the invention (curve n)).

(5) FIG. 3 depicts the two curves of power supplied (in W) as a function of time, using the regulations currently employed (curve o)) and according to the invention (curve p)), the hatched area highlighting the difference in power supplied according to the invention, especially during the first moments of pull down.

DETAILED DESCRIPTION OF THE INVENTION

(6) The approach of the invention of employing a far greater pinch during pull down (FIG. 1) and the very positive outcome of such an approach can therefore be clearly seen: with a pull down time which is faster by virtue of the invention (FIG. 2): an approximately 30% reduction in the pull down time can be seen (whether for temperatures close to 4° C. for fresh produce or negative temperatures for frozen products); which can be explained unambiguously by the difference in power transferred to the system by virtue of the invention (the hatched part in FIG. 3); at least 25% additional power is transferred during the pull down phase. this regulation also enables savings in cryogen to be realized, notably during the pull down phase, given that this phase does not last as long by virtue of the present invention. Experiments conducted by the applicant company have also demonstrated that by virtue of the present regulation, a drop in consumption is recorded for refrigerated transport scenarios for which the total duration of the round (pull down and hold) does not exceed 6 to 8 hours.

(7) FIG. 4 depicts an exemplary refrigeration truck for transporting heat-sensitive products according to the present invention. As shown, refrigeration truck 1 provides product storage chamber 2, reservoir of a cryogenic fluid 3, heat exchanger system 4, air circulation system 5, temperature sensors 6, and valves 7.

(8) As will also be clearly apparent to those skilled in the art, the invention as has just been described applies to the case of a single chamber within a truck but also to the case of several product storage chambers within a truck, and the invention therefore allows the temperature within each of these chambers to be regulated, each of the chambers being equipped with an exchanger system, each of the chambers having to comply with its own internal reference T.sub.ref according to the products it is to store, the control system measuring in real time the temperature internal to each chamber T.sub.int, that of the cold vapors leaving all or some of the exchangers of the exchanger system of each chamber (T.sub.fluidoutlet), the pinch associated with each chamber, etc.

(9) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

(10) The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

(11) “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of”or “consisting of” and remain within the expressly defined scope of “comprising”.

(12) “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something, The step may be performed by any actor in the absence of express language in the claim to the contrary.

(13) Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(14) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(15) All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.